A woman was found alive in the rubble 13 hours after a building collapsed in downtown Philadelphia -- killing at least six people and injuring more than a dozen others.

The collapse at 2140 Market Street in Center City happened around 10:40 a.m. on Wednesday when a four-story building came down on top of a two-story building, which housed a Salvation Army Thrift Store. Early reports from Philadelphia Police indicate that the collapse may have been the result of an industrial accident, as construction crews were working on the nearby structure.

Around 6:30 a.m. the next morning rescue efforts at the scene ended after 13 people were rescued and six found dead in the rubble.

One woman was found dead and 13 people were rescued from the rubble during the day. Mayor Michael Nutter said the woman was 35 years old. Sources close to the investigation say the woman was a cashier at the thrift store and that Wednesday was her first day on the job.

“Our thoughts and our prayers go out to those who lost their lives, and their families,” said Nutter.

Crews continued to dig through the night with the help of search dogs to see if anyone else remained trapped beneath the rubble. They found five more people dead, a man and four women, in the rubble Wednesday night. According to officials, all six people who died were inside the store at the time of the collapse. Darby Borough Police Chief Robert Smythe identified one of the victims as 68-year-old Borbor Davis of the Darby Borough. Davis, originally from Liberia, West Africa, worked at the thrift store and spoke to his wife on the phone at 10:30 a.m., 15 minutes before the building collapsed.

(Picture: 68-year-old Borbor Davis and his wife)

As crews continued to search the rubble, officials say 61-year-old Myra Plekam, who was trapped underneath, reached out and grabbed the hand of a firefighter. She was pulled out around midnight, making her the 14th person rescued. She was taken to the Hospital of the University of Pennsylvania where she remained in critical condition Thursday morning.

"She was talking to the firefighters as they were recovering her," said Michael Resnick of the Philadelphia Fire Department.

Nutter said the search is still active and will continue until crews are absolutely certain no one else is inside the rubble.

The 13 rescued victims were taken to local hospitals. Most of the injuries are minor. The Hospital of the University of Pennsylvania treated six of the 13 victims. A spokeswoman from the hospital said five of those victims were stable while Plekam remained in critical condition. Two of those victims have been released.

Rescue crews could be seen digging through the debris and brought in at least two pieces of heavy machinery to help move debris.

"I've never encountered anything like this before anytime in my life, and I don't want to see it again," said Vey, who was driving down 22nd Street right before Market and saw the building come down. "I feel really lucky. That brick landed in my passenger seat. Lucky for the rain guard on my window that saved me from getting hit."

Ordinary people took part in the rescue efforts as well. Roofers from a nearby building hustled over after the collapse and started pulling people out of the basement.

"They were pretty banged up," one of the roofers said.

The Salvation Army sent its own disaster response team to the site to help survivors and first responders. The organization sent out a statement saying, "Our No. 1 concern is for the safety of our customers and the employees who were involved."

Market Street was closed from 18th to 30th Street for most of the day but the zone was made smaller by Thursday morning as only the roads within a couple blocks of the collapse remained closed.

Fire officials say the building next door to the collapse was under demolition. According to the demolition permit from Philadelphia's Licenses and Inspections, that building was a four-story structure. The demolition contractor is Griffin Campbell Construction.

A man, who did not want to be identified, recorded video of the demolition of the building on Sunday and sent it to NBC10.com.

OSHA officials said they were aware of the incident and would be launching an investigation. The Department of Labor is also investigating.