The RCMP issued a Canada-wide warrant for the suspect after a "large quantity" of chemicals were discovered inside two homes in the Halifax area, Cpl. Greg Church said, though he declined to specify how many were found.
The suspect was arrested without incident at the Chimo Hotel and taken into custody after Ottawa police found his vehicle, Church said. He has not been charged.
The Mounties in Nova Scotia, who are handling the investigation, declined to name the man under arrest. But the manager of the man's ex-wife said police told her the suspect's identity.
Nick Furris said Shannon Miller, a former Olympic gymnast for the U.S., was told by police that her ex-husband, Christopher Phillips, was arrested in the incident.
"Upon hearing the recent news surrounding Christopher Phillips, my prayers immediately go to the safety of those around him," Miller said in a statement.
"I'm thankful that the brave men and women of the Ottawa police department and other law enforcement agencies were able to apprehend him and defuse the situation."
Church said some of the chemicals found in Halifax were labelled and confirmed to be "volatile and dangerous," while other chemicals have yet to be identified. He said a chemist will be brought in to help with the police investigation.
An explosive disposals unit, forensic identification experts and hazardous material crews were also enlisted to help with the investigation in Halifax, where evacuations in the communities of Cole Harbour and Grand Desert were ordered Tuesday as a result of the chemicals discovery. The evacuation of four homes within a 250-metre radius of a cottage in Grand Desert remained in effect Wednesday night.
David Croft, a resident of Grand Desert, watched as hazardous material teams worked near the small red cottage where chemicals were discovered.
Croft said people in the area found the man who came and went from the residence to be unfriendly.
"I don't consider this person my neighbour. I don't know him," Croft said. "I only spoke to him once in the past so I can't really know much about him, but I know he wasn't very friendly."
He said families in the area were concerned to hear there were still chemicals in the residence as of Wednesday evening.
"It's a concern for our neighbours and family for anything like this to take place. Nobody wants to think this is in their backyard."
RCMP investigators from Nova Scotia are travelling to Ottawa to interview the suspect, Church said.
In Ottawa, police said they found no hazardous materials following an overnight evacuation of the Chimo Hotel in the city's east end and there were no concerns for public safety.
Const. Chuck Benoit of the Ottawa police said there's no information suggesting there was a threat to national security or a connection to terrorism.
Benoit said the Ottawa police investigation began Tuesday at about 10:15 p.m. and a perimeter was established around the eight-storey hotel, describing their involvement in the investigation as "complex."
He said guests had to be evacuated from the hotel quietly and officers had to be careful not to alert the suspect, who was checked in to a room on the sixth floor of the hotel, while the evacuation was taking place.
"We are very fortunate that that went on so peacefully, and a lot of co-operation from the public that were inside, as well as the employees," he said.
Police closed all streets surrounding the hotel and asked the public to avoid the area. Benoit could not say how many people were involved in the Ottawa evacuation, but the Chimo Hotel website says it has 256 guest rooms.
The investigation in Halifax began after RCMP were alerted to a suspicious package in the neighbourhood of Cole Harbour, eventually leading to the evacuation of homes in that area on Tuesday morning.
The package was determined to contain hazardous materials, but not explosives, the RCMP said on their Twitter account.
Hours later, the Mounties ordered another evacuation in the Grand Desert area, about 35 kilometres northeast of downtown Halifax.
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