Rescue crews are preparing to take "more extreme measures" to continue search and recovery efforts at a badly damaged Elliot Lake, Ont., mall, an emergency official says.

"We are moving to more extreme measures to move this forward," said Elliot Lake fire Chief Paul Officer. "We're hopeful that we can get some success going here."

Part of the mall roof collapsed on Saturday, but since then, beams and slabs have been falling too, CBC's Ioanna Roumeliotis said. The changing conditions hampered search and rescue efforts and eventually made it too dangerous for crews to be near the "totally unsafe" building, a rescue official said earlier Monday.

The decision deeply angered some local residents, who said that the effort should continue. Some local people even volunteered to go in themselves, but an EMS spokesman later said that couldn't be done.

A woman checks out the damage after Saturday's roof collapse at the Algo Centre Mall in Elliot Lake, Ont. (Cora Richer/Canadian Press)

The situation at the Algo Centre mall remains dangerous, and rescue workers won't be going into the area, CBC's Natalie Kalata reported Monday night. Instead, crews will work with engineers to try to find a method of entry into the badly damaged space.

Some options include trying to remove two slabs of concrete on the stairwell and escalators.

But exactly how — or when — the teams would proceed with a new process was not immediately clear.

The news of the renewed effort came as Ontario Premier Dalton McGuinty said he had spoken to Emergency Management Ontario and the search and rescue team. McGuinty said he "instructed them to determine if there is any other way possible to reach any victims without endangering our rescuers, including the use of equipment to dismantle the building from the exterior."

It's also not clear exactly how many people are trapped, but police said earlier Monday that at least one person was dead. Officials had previously said that there were tapping sounds heard Sunday. Sounds that could be breathing were detected early Monday, but officials weren't able to comment on that person's condition as the day wore on.

Officials have not released any names of those caught in the collapse.

But Gary Gendron told CBC News that he believes the tapping was his fiancée, 37-year-old Lucie Aylwin, who many believe was working part time at a lottery kiosk when the roof caved in. Gendron, told CBC News he knows in his heart it was her who made the tapping sound, and that he's holding out hope that she's alive.

"I want her out of there. They're giving up," he said earlier in the evening, when it appeared efforts had stalled.

Provincial police said at an afternoon press conference that 20 people were still reported missing by their families. It wasn't clear if that number had changed yet again, as the number of people who remain unaccounted for has changed several times since Saturday.

"I believe we owe it to the families waiting for word of their loved ones to leave no stone unturned. We owe that to the people of Elliot Lake too. Ontarians expect nothing less," McGuinty said in a statement.

After the initial news conference, about 50 people gathered outside city hall to urge officials to resume the search, while some went to the mall to protest. The local newspaper said the crowd was chanting, "Rescue missions never end, save our family and friends."

Later Monday night, crowds gathered outside the damaged structure. They sang Amazing Grace and lit candles, saying they wouldn't give up hope.

Safety concerns remain

The search effort at the Algo Centre Mall was called off because of mounting safety concerns, including the threat of another collapse, an official said earlier Monday.

Bill Neadles, with the Heavy Urban Search and Rescue Team from Toronto, said engineers told him the Algo Centre Mall is under strain and too unstable for rescuers to enter safely. Neadles said crews were facing increasingly precarious conditions as they combed the debris for signs of life.

An unstable escalator that forced crews to remove their cranes from the site earlier in the day continued to separate from its supporting beams as the day progressed, he said.

"Realistically, the engineer's telling me he doesn't understand why it hasn't collapsed already," Neadles said. "The building is … totally unsafe."

"Our team is certainly not happy," said Neadles. "I'm not happy, nobody's happy that we have to stop work. But that's unfortunately the way we've had to end this situation."

Neadles said at the time that local officials would resume control of the site, which is under investigation by the Ontario Ministry of Labour. He said ministry officials would issue an order for at least part of the mall to be demolished, but that will likely be delayed.

When asked how many people they believe are inside the rubble-filled portion of the mall, police said they cannot account for two people. There could be more, as many more people were reported as unaccounted for by family members.

The number of people missing or unaccounted for has fluctuated greatly since the collapse, with some names being taken off the list and others added, police Insp. Percy Jollymore noted earlier.

"Overnight [from Sunday] it's grown again, with people calling in, worried about people they haven't been in touch with … I caution, it goes up and down," Jollymore said early Monday.

Local residents who gathered for the news conference wept, while some said a mine rescue team should be dispatched to the scene.

Throughout, mall manager Rhonda Bear said the owners wanted to see the rescue continue.

Bear told CBC that the owners are "very devastated" and that the owner was so upset he could barely speak.

"They are on the people’s side on this one," Bear said.

Elliot Lake Mayor Rick Hamilton said he was "hopeful" that the rescue effort could start up again.

"We will be making sure that they exercise every possible avenue to ensure that that rescue is facilitated as quick as possible," Hamilton told the CBC's chief correspondent Peter Mansbridge in an interview Monday night.

Hamilton added he understood why residents were frustrated.

"I can't blame them, and that's why we are making every effort possible to make sure we can expedite the process as quickly as possible," he said.

In a Monday morning interview with CBC News Network, the mayor would not talk about the building's structural safety and insisted the focus was only on the rescue effort: "There certainly may be time in the future to deal with that."

In the aftermath of the collapse, many residents said the mall has had a history of problems dating back to 2005 with roof leaks, flooding and falling tiles.

CBC Community member Nikki Lafleur posted this comment: "Pieces of the roof have been falling on shoppers for a long time. The people of Elliot Lake have been saying something like this would happen and they keep putting a Band-Aid on it," she said.

Asked about his own visits to the mall and whether he noticed any possible problems with the mall's roof, Hamilton said that while he and his family shopped there, he's "just dealing with the matter now at hand which is the actual rescue."

Maintenance work on roof

The collapse happened around 2:20 p.m. ET Saturday. There are reports two cars went through the roof. Twisted debris could be seen near a set of escalators, food court tables and lottery kiosks.

Yves Berube, who runs a jewelry store in the mall, said he had just stepped out to have a cigarette when the floor collapsed, taking off the front part of his shop.

"I didn’t even get a chance to light it [and] then all of a sudden, boom, everything caved in behind me," he told CBC News.

"So I went running back in to see, and that’s when I saw this monstrous hole.… There was one lady, when I went back in, she was still sitting in her chair. There were pieces of concrete and steel girders all around her.

"I was looking up and seeing the sky where there should have been a roof."

Bear, the Algo Centre Mall manager, told CBC News earlier Monday that repair and maintenance work has been done on sections of the building's roof over the last year but not in the area that collapsed.

She also said the shopping centre's owner completed an engineering and structural study of the building last month, but it turned up nothing.

However, many local residents insist the building was in need of repairs, and a local newspaper, the Standard, has previously reported that the mall's owners embarked on a massive overhaul of its roof several years ago due to leaks.