(CNN) -- Authorities in Elliot Lake, Ontario, on Sunday were searching the rubble left by a roof collapse a day earlier at a large shopping mall.
The collapse is believed to have killed one person and at least one other may be trapped, according to Kate Matuszewski, public information officer for the city of Elliot Lake. Twenty-two other people suffered non-life-threatening injuries in the incident, which occurred around 2:20 p.m. Saturday at the Algo Centre Mall in southern Ontario.
"We have obtained some visual information relating to a visual of a hand and a foot, which is our grounds for the suspected casualty in this case," said Inspector Percy Jollymore of the Ontario Provincial Police. Searchers have not reached the suspected victim and no positive ID has been made, he said.
Pictures of the scene show a portion of a rooftop parking deck that collapsed, sending metal and concrete debris crashing into the atrium of the mall.
Search dogs were brought in to assist in the rescue, but the instability of the building was slowing the effort, officials said, estimating it would take another 10-12 hours before they could shore up the remaining structure.
"We have to do a very slow and tedious but safe entry" into the affected area, said Bill Needles, incident commander for Toronto's heavy urban search and rescue team. Needles described the effort as a "very, very dangerous situation."
Authorities were alerted to a possible survivor Sunday morning when they heard tapping sounds from inside the rubble. No further contact was made and camera equipment failed to locate the possible survivor before rescuers were forced to suspend the search due to the structural instability, Needles said.
Shoppers and mall employees described a chaotic scene.
"All of a sudden I started getting hit by some of the rubble. I turned around. I saw other people in the food court running out of the doors. I remember seeing the concrete. There was instantly so much dust, first you saw (the food court), and then you didn't," Elaine Quinte, owner of the Hungry Jack's restaurant at the mall, told CNN Canada affiliate CBC.
Jean-Marc Hayward told CBC on Sunday that he was "still shaken up about it."
"First thing after it all happened, you're trying to take it in and next thing you know everyone is trying to get outside and one guy is saying, 'There's no way out, there's no way out,'" he said, according to CBC.
CNN's Chris Boyette contributed to this report.