(PHILADELPHIA) -- After hours of searching, rescuers late Wednesday located a person alive in the rubble after a four-story building in central Philadelphia collapsed Wednesday morning.
A 61-year-old woman from the Kensington section of Philadelphia was pulled from the rubble shortly after 11:30 p.m. Wednesday, according to ABC News affiliate WPVI-TV. She is said to be in critical condition.
The development came Wednesday night after Mayor Michael Nutter announced six fatalities after the building collapse.
Fourteen people had been pulled from the rubble during rescue efforts Wednesday afternoon. At least 13 people were transported to hospitals with minor injuries, according to authorities.
Police have declined to comment on the status of the fourteenth individual pulled from the debris.
Fire commissioner Lloyd Ayers said Wednesday afternoon that emergency workers would continue searching for victims buried in the debris by using two police dogs to trace human smells and additional workers to sift through the pile of rubble.
"We're getting fresh personnel and staffing here to dig and we've had two dogs to come out and work the pile to locate others so we know exactly where to dig," Ayers said at a press conference earlier Wednesday.
Ayers said he expected workers to continue digging at the site for 12 to 24 hours, until they were sure that no individuals remained buried.
"Let's again keep in mind that we did not know and do not know how many people were actually in the thrift store," Mayor Michael Nutter said Wednesday afternoon. "That is why the fire department search and rescue operation continues."
The building was in the process of being demolished when an exterior wall that it shared with an adjoining building fell outward, collapsing into the adjoining two-story building that housed a Salvation Army Thrift Store. The thrift store was damaged but is still standing.
Many of the injured victims were shoppers at the thrift store, according to ABC News affiliate WPVI. At least one injured individual was a crane operator working on the demolition of the building, and one individual has already been released from a hospital, according to WPVI.
The vacant mixed-use commercial building was in the process of being demolished when it collapsed, according to city inspector Carlton Williams. Authorities are unsure how many construction workers were at the site when the building collapsed.
"We want to be sure to keep the focus on the firefighters that are actively engaged in search and rescue," Nutter said earlier Wednesday. "We had a significant number of people on the scene, and we will continue this operation until we are certain that anyone who was in the building has been taken out of building and is recovered."
Firefighters were first dispatched to the building at 10:43 a.m. and arrived at 10:45 a.m. to begin working, Ayers said.
A 10-block stretch of Market Street, which runs through the city, was shut down for the rescue effort.
Williams said that both the building's owners and the contractors had all of their permits and paperwork in order and up to date, and the building had no prior code violations.
Copyright 2013 by ABC News Radio.