SURFSIDE, Fla. (NewsNation Now) — Rescue crews are still combing through the wreckage of the fallen 12-story condo in Florida hoping to find more survivors in areas they call “voids.”

Former Miami-Dade rescue chief Dave Downey told The Donlon Report the teams on the ground are “chasing sounds” – hoping a creak or a moan might lead them to somebody they can help. So far, four people have been confirmed dead and 159 are still missing.

“Sometimes you think you hear something crying, sometimes you think you hear somebody’s breathing,” Downey said. “Sometimes you you know, just hear movement, you know, the bit building is settling, the concrete is moving, the steel is moving.”

This is happening above the rubble and underneath it. Crews are going in through the parking garage looking for voids or empty spaces where someone could be trapped.

“The voids can be created by furniture falling over refrigerators, even beds, we’ve tunneled through beds to locate survivors,” he said.

Another danger is the rest of the structure could come down at a moment’s notice. Some crew members are using cherry pickers to remove overhanging debris that could fall, called “widow makers.”

“Heavy equipment is going to be used surgically to remove pieces, large pieces of concrete and steel in order to try to uncover some other void spaces,” Downey said. “Every time you move something, there’s another reaction. And we’ve got an entire building still standing, that is in danger of collapse.”

Dogs are also part of the search team, and Downey said they actually get sad when they are not able to find people who are trapped. He said the rescuers sometimes will stage people in the disaster area to give the dogs someone to find.

Downey added the rescue operation will keep going until the last possible moment.

“My heart aches for those victims and for those families, and I just want them to realize that nobody on that pile has given up hope,” he said.