Nearly one year ago, life as they knew it changed forever for residents of one Allentown neighborhood.

Thursday will mark the first anniversary of a gas explosion and fire that destroyed a row of homes and killed five people. An empty lot is all that is left of the eight homes that once stood there.

The Public Utility Commission is still investigating the incident, which is believed to be the result of aging cast iron under the streets of Allentown.

On the night of February 9, 2011, the explosion rocked 13th and Allen streets.

"Fifty foot flames, giant hole, debris still falling from the sky," said 2nd Battallion Chief Bill Held, Allentown Fire Department.

Fire crews spent the night battling the inferno.  The neighborhood and nearby Gross Towers were evacuated.

"We have confirmed there have been five deaths," said Scott Grim, the Lehigh County coroner, on the day after the expolsion.

The victims ranged in age from four-months-old to 79-years-old.

Beatrice and William Hall lived in their home at 544 North 13th St. for 50 years. The other three victims, Ofelia Ben, 69; her great-grandson, 4-month-old Matthew Vega; and Matthew's mother, Katherine Cruz, 16, lived next door.

Investigators linked an 83-year-old cast iron gas main to the blast, but UGI and the Public Utility Commission have yet to release their official findings.

Matthew Bainbridge, But Allentown fire marshal, said he remembers what he saw when the pipe in question was unearthed:

"I observed two wooden blocks underneath the pipe that may have created a fulcrum for the pipe to eventually crack," said Bainbridge.

The pipe is part of an aging gas line network that weaves its way across the Lehigh Valley and throughout the state.

"It is a time bomb," said Pa. Sen. Lisa Boscola, D-Lehigh Valley. "It's definitely a time bomb."

Boscola said Reading-based UGI needs to get old pipes out of the ground faster.

UGI has been aggressive in its infrastucture replacement, said Rob Powelson, chairman of the PUC.

"That's not necessarily the case for other gas companies here in Pennsylvania," said Powelson.

Since 2000, UGI has replaced more than 290 miles of cast iron pipeline in its entire service area, the company said, adding that fewer than 440 miles of cast iron lines remain in its system.

Utilities said they can't move faster without passing on the cost to consumers. Lawmakers have been grappling with the issue.

Pennsylvania House Bill 1294 seeks to charge gas customers an extra fee to replace aging pipes.

"Now, because people are being blown up, there's legislation that says this charge will be on your bill and then that will help pay for the infrastructure replacement," said Boscola.

Residents who lost loved ones and homes in the blast are struggling to move on with their lives.