PHILADELPHIA (CNN) - There will be a "wide-ranging" investigation into why a building collapsed in Philadelphia, killing six people, Mayor Michael Nutter told reporters Thursday morning.
Rescue workers have searched about 75% of the site where the side of a four-story structure collapsed at about 10:45 a.m. Wednesday, toppling onto an adjacent Salvation Army store, Nutter said.
At least 14 people were injured, authorities have said.
The mayor said all the names of those who died will be released by the end of the Thursday.
But he asked that members of the media "respect" what he called "humanity time" and hold off trying to contact relatives of the dead because family members are still trying to be the ones to deliver the awful news to their loved ones. Behind him, a large crane and workers were trying to dismantle the wreckage. There has been no let-up in rescue workers' attempts to find survivors.
Philadelphians shouldn't be concerned if they take a trolley near the area, he said, because transit authorities have slowed it down as a precaution as the massive rescue effort continues.
Wednesday night crews worked tirelessly under LED lights, combing through the rubble with cameras, microphones and motion detectors.
There was a brief jolt of joy when, shortly before midnight, 61-year-old Myra Plekam was pulled out.
She was freed some 13 hours after the first reports about the collapse came in to authorities, which Nutter said was 10:43 a.m. She's in critical condition at the Hospital of the University of Pennsylvania.
Responders were on the scene two minutes after getting the calls.
"It feels outstanding to be able to pull somebody (out) alive," said Michael Resnick, the city's public safety spokesman.
Nutter told reporters late Wednesday night that authorities didn't know how many people were in the store at the time of the accident.
He was concerned the collapsing wall may have also hit people walking by outside.
Wednesday night, more than a third of the rubble still needed combing through, Fire Commissioner Lloyd Ayers said.
And so responders searched on. Slowly. Carefully.
Empty dump trucks came and left with their buckets filled with cleared debris. More arrived.
Crashing sound, shaking earth
Boskie Shah had stopped to watch the demolition work just before the side of the building fell over around 10:40 a.m. ET Wednesday.
A construction crane bumped the building twice, before it swayed, he said.
"The right wall leaned toward 22nd Street and collapsed on the thrift shop."
Debris spread out, and a dust cloud rose through the air. Shah took a photo and later uploaded it to CNN iReport.
Jordan McLaughlin felt the earth shake under his feet when the wall came down, he told CNN affiliate KYW.
"There was people that actually fell over," he said. "People started screaming, they ran across the street. There was people inside the building, you heard them scream."
He said he helped two people out of the building. Other bystanders, including construction workers, helped four or five others out.
Another witness, Ari Barker, said he was in his office across the street when he heard "a rumbling, a very unusual sound." He rushed to the window to see a plume of dust rising from the debris.
Some saw it coming
"I knew that was going to collapse sometime soon, and it did today," Patrick Glynn told CNN affiliate WPVI.
"For weeks, they've been standing on the edge, knocking bricks off, pieces off, you could just see it was ready to go at any time. I knew it was going to happen. I seen it. I said it 10 times. Ask these guys. Every day, I said, 'It's gonna collapse, it's gonna collapse.'"
Minerva Pinto works nearby. She and her coworkers thought the building looked precarious in the days before the collapse.
"We'd all seen in the past week that the building was really unstable because of the demolition," she told CNN's iReport.
But city officials said there were no known violations at the site.
"No violations, no complaints that we're aware of, and all permits were valid," Nutter told reporters earlier.