AIRDRIE, Alta. - Investigators brought in a dog and a police motorboat on Sunday as they shifted their search for a five-year-old Calgary boy and his grandparents to a field and a slough north of an acreage.

The area police were focusing on Sunday is about a kilometre north of the acreage near this Calgary bedroom community that police combed on Saturday.

Yellow police tape blocked off an adjacent road and a half dozen officers and a dog walked through a field to the edge of a large slough. Moments later a Calgary police boat was towed into continue the search while a police helicopter searched overhead.

Earlier in the day police revealed they had released an individual taken into custody at the acreage Friday night.

Calgary police said he remains a "person of interest" and several police units will continue to search a residence connected to him on the outskirts of Airdrie.

Investigators say that, given the size of the property, the search is likely to continue throughout Sunday and into Monday as they search for clues in the disappearance a week ago of Nathan O'Brien and his grandparents — Alvin and Kathy Liknes.

Acting on a tip police arrived at the property late Friday night and found a green Ford F-150 truck similar to one spotted in a video taken near the Liknes home.

Police say they are trying determine if the truck, the property, or the man taken in for questioning, are linked to the investigation.

Nathan and his grandparents disappeared on Monday after the couple held an estate sale, and police have said there was evidence of a violent incident in the Liknes's home.

Police say they want to hear from anyone who has any information regarding the whereabouts of the missing people or recognizes the pickup that was captured on video in the area of the grandparents' home.

Investigators say an Amber Alert remains in place and is continuing to provide police with tips from the public.

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  • Mourners have placed flowers, notes and teddy bears at an impromptu memorial for Nathan O'Brien and his grandparents, Alvin and Kathryn Liknes, at the Liknes home in Calgary, Alta., Tuesday, July 15, 2014.

  • Flowers and teddy bears are shown at an impromptu memorial for Nathan O'Brien and his grandparents, Alvin and Kathryn Liknes, at the Liknes home in Calgary, Alta., Tuesday, July 15, 2014. A man who has been under investigation in the disappearance of a Calgary boy and his grandparents has been formally charged with their murders.

  • Bobbi-Jo Zimmer, from High River, Alta., and her children, left to right, Tayvon, two, Braylon, seven, and Dawson, nine, place flowers at an impromptu memorial for Nathan O'Brien and his grandparents, Alvin and Kathryn Liknes, at the Liknes home in Calgary, Alta., Tuesday, July 15, 2014.

  • Mourners have placed flowers, notes and teddy bears at an impromptu memorial for Nathan O'Brien and his grandparents, Alvin and Kathryn Liknes, at the Liknes home in Calgary, Alta., Tuesday, July 15, 2014.

  • Kelley MacAuley observes a memorial after placing flowers at an impromptu memorial for Nathan O'Brien and his grandparents, Alvin and Kathryn Liknes, at the Liknes home in Calgary, Alta., Tuesday, July 15, 2014.

  • Jennifer Kohut, centre, embraces her sons Axton, left, three, and Cadon, five, after placing flowers and toys at an impromptu memorial for Nathan O'Brien and his grandparents, Alvin and Kathryn Liknes, at the Liknes home in Calgary, Alta., Tuesday, July 15, 2014.

  • Douglas Garland is escorted into a Calgary police station in connection with the disappearance of Nathan O'Brien and his grandparents in Calgary, Alta., Monday, July 14, 2014.

  • Douglas Garland is escorted into a Calgary police station in connection with the disappearance of Nathan O'Brien and his grandparents in Calgary, Alta., Monday, July 14, 2014.

  • Douglas Garland is escorted into a Calgary police station in connection with the disappearance of Nathan O'Brien and his grandparents in Calgary, Alta., Monday, July 14, 2014.

  • Douglas Garland is escorted into a Calgary police station in connection with the disappearance of Nathan O'Brien and his grandparents in Calgary, Alta., Monday, July 14, 2014.

  • Calgary Police Chief Rick Hanson says first and second degree murder charges are being filed in connection with the disappearance of Nathan O'Brien and his grandparents at a news conference in Calgary, Alta., Monday, July 14, 2014.

  • Calgary Police Chief Rick Hanson says first and second degree murder charges are being filed in connection with the disappearance of Nathan O'Brien and his grandparents at a news conference in Calgary, Alta., Monday, July 14, 2014.

  • Calgary Police Chief Rick Hanson says first and second degree murder charges are being filed in connection with the disappearance of Nathan O'Brien and his grandparents at a news conference in Calgary, Alta., Monday, July 14, 2014.

  • People comfort each other at a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • People comfort each other at a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Volunteers prepare candles at a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • A photo collage of the Liknes and O'Brien family is displayed as neighbors, friends and relatives hold a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Rod O'Brien, centre, tears up as he looks at a photo collage of the Liknes and O'Brien family during a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • A photo collage of the Liknes and O'Brien family is displayed as neighbors, friends and relatives hold a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Rod O'Brien, centre, father of Nathan O'Brien, attends with neighbors, friends and relatives, a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Jennifer O'Brien, left, mother of Nathan O'Brien, attends with neighbors, friends and relatives, a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Rod O'Brien, and Jennifer O'Brien attend a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Neighbors, friends and relatives hold a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Rod O'Brien, right, and Jennifer O'Brien, centre, attend a candlelight vigil for missing Calgarians Nathan O'Brien, five, and his grandparents Alvin and Kathryn Liknes in Calgary, Alta., Thursday, July 10, 2014.

  • Police investigators comb a hay field north of Airdrie, Alta., Monday, July 7, 2014, looking for clues to the disappearance of three people.

  • Police investigators use an inflatable raft in a slough north of Airdrie, Alta., Monday, July 7, 2014, looking for clues to the disappearance of three people.

  • Police investigators prepare to search a hay field north of Airdrie, Alta., Monday, July 7, 2014, looking for clues to the disappearance of three people.

  • Police investigators prepare to search a hay field north of Airdrie, Alta., Monday, July 7, 2014, looking for clues to the disappearance of three people.

  • Police investigators prepare to search a hay field north of Airdrie, Alta., Monday, July 7, 2014, looking for clues to the disappearance of three people.

  • Police investigators prepare to search a hay field north of Airdrie, Alta., Monday, July 7, 2014, looking for clues to the disappearance of three people.

  • Police investigators at a rural residence north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Police investigators comb a hay field north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Police investigators comb a hay field north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Police investigators comb a hay field north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Police investigators comb a hay field north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Police investigators comb a hay field north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Police investigators at a rural residence north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Police investigators at a rural residence north of Airdrie, Alta., Saturday, July 5, 2014, looking for clues to the disappearance of three people.

  • Rod O'Brien wipes his tears while holding a butterfly made by his son as he speaks to the media about his son Nathan O'Brien and his grandparents Alvin and Kathryn Liknes during a press conference in Calgary on Wednesday, July 2, 2014.

  • Rod and Jennifer O'Brien show their emotions as they speak to the media about their son Nathan O'Brien and his grandparents Alvin and Kathryn Liknes during a press conference in Calgary on Wednesday, July 2, 2014.

  • Rod and Jennifer O'Brien left, look on as Jeff Liknes, second from right, speaks to the media about his nephew Nathan O'Brien and his parents Alvin and Kathryn Liknes during a press conference in Calgary on Wednesday, July 2, 2014.

  • Jennifer O'Brien holds a piece of her son's clothing while speaking to the media about her son Nathan O'Brien and his grandparents Alvin and Kathryn Liknes during a press conference in Calgary on Wednesday, July 2, 2014.

  • Jennifer O'Brien holds a piece of her son's clothing while speaking to the media about her son Nathan O'Brien and his grandparents Alvin and Kathryn Liknes during a press conference in Calgary on Wednesday, July 2, 2014.

  • Rod O'Brien wipes his tears while holding a butterfly made by his son as he speaks to the media about his son Nathan O'Brien and his grandparents Alvin and Kathryn Liknes during a press conference in Calgary on Wednesday, July 2, 2014.

  • Rod and Jennifer O'Brien show their emotions as they speak to the media about their son Nathan O'Brien and his grandparents Alvin and Kathryn Liknes during a press conference in Calgary on Wednesday, July 2, 2014.

  • Nathan O'Brien is described as three feet tall, curly blonde hair, brown eyes, and was last seen wearing peach-coloured shorts and a blue-striped hoodie.

  • Kathryn Liknes is five-foot-three-inches tall, 120 pounds with reddish-brown hair and green eyes.

  • Alvin Liknes is six feet tall, 200 pounds with grey and blond hair and was wearing black shorts. Alvin has a distinctive walk.

  • Calgary police investigators check out the home where five-year-old Nathan O'Brien and his grandparents Alvin and Kathryn Liknes disappeared, in Calgary, Alta., Wednesday, July 2, 2014.

  • Nathan O'Brien and his grandmother Kathy Liknes are shown in a Calgary Police Service handout photo. Calgary's police chief questions whether a reward would help the investigation into the disappearance of a five-year-old boy and his grandparents.

  • Police tape cordons off the home where five-year-old Nathan O'Brien and his grandparents Alvin and Kathryn Liknes disappeared, in Calgary, Alta., Wednesday, July 2, 2014.