Search and rescue crew members heard "tapping" from within the rubble at the Algo Centre Mall, but were unable to reach two women killed in the roof collapse at the Elliot Lake, Ont., shopping centre.

Jim Lawson, a search manager with the Heavy Urban Search and Rescue team, spoke to CBC News about the recovery experience along with Chris Rowland, a rescue squad leader with the unit. On Wednesday, both men watched the bodies of two female victims brought out from the ruins.

Lawson was on the scene at 9:30 a.m. Sunday, when he recalled hearing what he believed to be signs of life from the rubble.

"We were calling out, asking anyone — if they were in there, if they could hear us — if they could tap," he said. "And we heard a tap. We looked at each other, kind of in a shocking way, and kind of said, 'Did you hear that?' And then we called for all quiet on the site and asked again and then there was a second tap."

Lawson said he made a third request.

"Third time I asked her to wait a second and then tap three times, and there was just one. Waited a second, but there was just one very faint tapping at that time."

Rescue efforts were hampered by what officials deemed "precarious" conditions at the site, as experts feared removing sections of the building could cause more of it to topple, endangering the lives of rescue workers.

On Wednesday night, Ontario Premier Dalton McGuinty toured the excavation site in Elliot Lake, 150 kilometres west of Sudbury, and pledged to order a review of the emergency response.