Word of the dramatic development came after 11:30 p.m. Wednesday.
Reports from the scene indicated that firefighters and other rescue personnel began digging feverishly after feeling the woman's body in the rubble.
A short time later they were able to pull 61-year-old Myra Plekam of Kensington out of the wreckage. She was rushed to the Hospital of the University of Pennsylvania in critical condition.
The dramatic rescue came some 13 hours after the massive building collapse on Market Street - and after an evening when crews removed at least 5 bodies from the rubble, bringing the death toll to 6.
Philadelphia Mayor Michael Nutter confirmed the death toll in a late evening news conference at the site of the collapse.
Speaking shortly after 11:00 p.m., before the dramatic rescue, Nutter said city officials still do not know how many people were in the Salvation Army Thrift Store when it collapsed Wednesday morning, and that search teams will continue to work through the night.
"If anyone is still in that building," said Nutter, "they will find them."
Live video images from the 2100 block of Market Street showed rescue personnel gathering around the wreckage of the thrift store starting at 7:45 p.m. Wednesday.
Three rescue vehicles with lights flashing were parked near the collapse site. They were positioned in such a way as to prevent cameras from recording the scene. Rescue crews were seen moving toward the collapse site holding large tarps, presumably to block the view of cameras.
There was activity but no sense of urgency among the rescue personnel, suggesting that what was taking place was the removal of bodies.
Until that point, only one person, a 35-year-old woman, had been confirmed dead. Authorities have withheld her name at the request of her family.
Action News has learned that Wednesday was the woman's first day on the job at the store.
The collapse happened when a 4-story building at 2140 Market Street, which was being demolished, collapsed onto the two-story Salvation Army Thrift Store, located next door.
Nutter and Fire Commissioner Lloyd Ayers said on Wednesday afternoon that 14 people were removed from the scene.
Of the 13 injured, most were reported to have minor injuries.
Dan Gillis said he saw the collapse happen, saying "I was working across the street doing windows. They've been working over there for about a week now. It was a 30 foot wall, they started pulling on a piece of steel, and I seen the whole wall just waving back and forth, and as soon as they pulled that out, there was no stopping it."
The collapse brought down part of the thrift store and what looks like converted row homes attached to the back of the building.
Bystanders immediately jumped into action, helping assist the wounded before first responders arrived.
Emergency crews worked feverishly to find victims trapped in the rubble.
"Our firefighters are actively engaged in a search and rescue operation. It is delicate, this is dangerous work," explained Mayor Michael Nutter. "We're going to continue this operation until we are certain that anyone who was in the building has been taken out of the building and is recovered."
Mayor Michael Nutter is asking the public to please avoid the area from 20th Street to the Schuylkill River and Chestnut Street to the Ben Franklin Parkway.
According to officials, there was an active demolition on the 4-story building at 2140 Market by a Philadelphia-based company known as Griffin Campbell Construction. There were no existing violations on the property and the contractor conducting the demolition had a license.
PASSER-BY BECOMES FIRST RESPONDER
High school senior Jordan McLaughlin, of Chestnut Hill, was walking along the 2100 block of Market Street when he saw and heard the building collapse.
"It was like a boom. There was nothing before the collapse. You heard the backhoe hit the wall."
McLaughlin charged into the rubble to pull two injured victims to safety, disregarding his own.
He gave Action News this up-close and personal account.
"When we went into the scene, we said, 'Can you hear us? Can you hear us?' And then we got a response," he said. "I ended up helping get two people."
McLaughlin was not alone in suddenly becoming a first responder. Brian Mullens and Bill Rome were working nearby when they heard the boom and charged into action.
"We ran right around the corner. We saw a couple of people. The roofers who were working upstairs on the roof came running right behind us, and we started digging and pulling people out," said Mullens.
"We actually pulled a couple out of the basement. One of the roofers went down into the basement," said Rome. "The gentleman was very gutsy and went down and started handing people up to us. There was one woman who was trapped who we couldn't get out. She was in a pocket. We were waiting for the rescue people to come and move the stuff properly."
FIVE TAKEN TO JEFFERSON
Five victims of the collapse were taken to Thomas Jefferson University Hospital with minor injuries.
As of 5:00 p.m. Wednesday, none had been admitted. Two, a man and a woman, were released. Action News was there as Nadine White emerged from the hospital with relatives.
On Tuesday, Nadine celebrated her 54th birthday. Wednesday morning, she went to work at the Salvation Army Thrift Store at 22nd and Market.
About 45 minutes later, her family members say, Nadine was working near the back of the store when the walls came tumbling down.
She was partially buried in the rubble. One of her co-workers stayed with her until rescuers could dig her out.
Nadine suffered cuts and bruises and, along with four other victims, was taken to Jefferson.
When she was released at around 3:30 p.m. Wednesday, her family's main concern was getting her home safe and sound.
Jefferson officials have been tight-lipped about the five patients who were treated there. A hospital spokeswoman told Action News no extra trauma teams had to be called in to handle the victims.
FIVE OTHERS TREATED AT HUP
Another woman pulled from the rubble was among five people treated at the Hospital of the University of Pennsylvania (HUP).
"We can say she is stable but that's about it," said Dr. Patrick Kim of HUP.
Three other women were also brought in. All told hospital workers they were inside the Salvation Army store at the time of the collapse.
"They were saying they heard a loud noise and the ceiling began falling," said Dr. Elizabeth Datner of HUP.
The fifth person treated was a man who walked into the hospital on his own claiming to be a crane worker at the collapse site.
Doctors say none of the injuries were severe, despite the way the scene appeared. All the victims who came to HUP were alert and talking when they came in.
"Most of the injuries we're seeing are relatively minor, bruises, lacerations," said Datner.
"We can expect their physical injuries to heal up," said Kim. "Mental distress - they might be recovering from after something like this."
One person had been released as of 5:00 p.m. Wednesday. Two more were expected to be released by the end of the day.
Doctors planned to keep the woman who was pulled from the rubble and one other person in the hospital overnight for observation.
Stay with Action News and 6abc.com as more information becomes available.