"We are really grasping at straws right now. We don't know what the circumstances are surrounding Thelma's disappearance," Const. Eric Hofley told reporters Friday.
"We are hoping anybody with any type of information comes forward."
Thelma Krull was last seen on the morning of July 11, when she left her suburban home to go for a hike. She had planned to pick up a birthday cake for her grandson later on. She had no history of going missing, Hofley said.
Police and volunteers have scoured the area but found little to help — surveillance footage captured a brief shot of Krull walking near her home, and her glasses were discovered Tuesday near a community centre.
Police reissued a plea Friday for anyone else with home or business security cameras in the area to see if they have more footage of Krull.
They also released a photograph of two cyclists who were in the area at the time. The grainy pictures shows one cyclist with what appears to be a tennis racket. Hofley said the two are not considered suspects and are simply being sought in the hopes that they might have seen Krull.
The homicide unit has taken the lead on the case, although Hofley insisted it is still being treated as a missing person file.
"Multiple units across the service are actively involved in this investigation," he said.
Krull's husband, Robert, issued a public plea for information earlier in the week. He said there were no signs of trouble before Thelma disappeared — she had gone for the morning walk while he was still asleep.
Thelma Krull had started walking long distances in order to train for a seven-day hike in British Columbia.