PGW crews were originally called out to the 6900 block of Torresdale Avenue in Tacony at 7:19 p.m. due to a 12-inch high pressure gas main break.
Officials say while working the break something went wrong and the main ruptured around 8:30 p.m. causing an explosion.
5 people, 4 PGW workers and a firefighter, were taken to Aria Hospital Torresdale Division.
Commissioner Lloyd Ayers said in a late Tuesday night press conference, 3 of the PGW workers are in critical condition. The fourth PGW employee and the firefighter are stable.
The Action Cam was on the scene at the hospital as two ambulances brought in four of the victims; the fifth walked in for assistance.
It appears these victims have suffered very serious burns.
According to a hospital spokesperson, four of the victims will be transferred to the Temple University Burn Unit.
During the press conference, Ayers mentioned a fifth PGW worker was still missing. Just after 11:00 p.m., authorities told Action News, the PGW worker's body was found under the debris.
The explosion caused a massive fire to erupt.
RELATED: RAW VIDEO: Smoke fills Tacony sky A second alarm came in at 8:35 p.m. and just before 9:00 p.m., a third alarm was struck.
Two buildings caught fire as a result of the explosion.
Residents could not believe what they saw.
"While they were digging to get to the main, it blew up right there. I was 50 feet from it, it was unbelievable," witness Chris Labovitz said. "The fireball was 30, 40 feet high."
"We were right there?just as long as everybody is alright, all the properties can be replaced," witness Georgeanne Labovitz said.
The fire was placed under control by 11:00 p.m.
At least 30 people were evacuated while crews worked on the break prior to the explosion. Some were sent to the Disston Recreation Center at Glenloch and Disston streets.
Mayor Michael Nutter asked those affected to seek shelter with family and friends nearby.
The identities of the victims have not been released.