PHILADELPHIA (CBS) — Eight people, including three children, were injured following a row home explosion and collapse in Philadelphia Monday morning.

The incident happened at about 11 a.m. in the 400 block of Daly Street in South Philadelphia.

VIEW: Photos From The Scene

Chopper 3 HD was over the scene where one row home collapsed and two others partially collapsed following what witnesses are calling an explosion. The addresses of the homes impacted were 426-430 Daly Street.

The City has determined that an explosion occurred due to natural gas.

Neighbors said they heard a loud rumble and a strong odor of gas was noticeable shortly after the collapse.

Joe Szymborski said he was laying in bed when he heard the explosion. “I threw on my shoes, ran down there and helped three people out of the house,” said Szymborski.

KYW Newsradio’s Steve Tawa reports that a worker who was burned in the basement of 428 Daly Street was having issues with a water heater as he renovated the unoccupied rowhome.

Suddenly, an explosion.

The contractor was the most seriously of all those injured. He was transported to the Hospital of the University of Pennsylvania in critical condition with burns, then transferred to the burn unit of Temple Hospital.

City officials say 70 homes on Daly and Wolf Streets were evacuated.

Investigators say a total of four adults and three children were injured and taken to Thomas Jefferson University Hospital, where they were treated and later released.

A spokesperson for Jefferson University Hospital said among the seven people treated there were a mother, a father, and a two-month-old baby who were inside 426 Daly Street, the home next to the collapse.

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An official with the Philadelphia Fire Department confirmed that the home that exploded was vacant and undergoing renovations.

In an exclusive interview with Eyewitness News, Dell Kean-Finney told us her husband Steve Finney is the owner of SCK Investments. In March, the firm bought the home at the center of this explosion at 428 Daly Street. Eyewitness News is told it was an investment property and as seen in these photos Eyewitness News obtained the home had been gutted, renovated and ready for sale.

“Truly, our prayers and our concerns are for anyone in any way to any degree has gotten hurt,” said Kean-Finney.

Crews with the Philadelphia Gas Works responded to the scene to turn off gas service in the area and PECO turned off electricity to homes on the street.

Fire officials say the incident was placed under control by 12:30 p.m. Evacuees were taken to a makeshift shelter at Taggart Elementary School at 4th and Porter Streets.

According to city officials, 428 Daly Street was a permitted construction site. The Fire Marshall, the Department of Licenses & Inspections (L&I), and the Philadelphia Gas Works (PGW) are currently investigating the cause of the gas leak.

“Three houses were demolished… We’ll decide whether to turn it over to the owners, to have their own contractors do the demolition or whether we do it ourselves,” said Steve Gallagher, L&I Chief of Contractual Services.

The collapse in South Philadelphia comes nearly two months after a collapse in Center City killed six and injured 13 (read more here).