Federal officials are investigating a Manor Township house explosion that left one UGI Utilities worker dead and three other people injured Sunday afternoon.

Officials from the National Transportation Safety Board were expected to arrive at the scene late Sunday, an official said. It wasn't immediately clear what prompted the state Public Utility Commission to turn over the investigation to federal authorities.

Workers were investigating a reported gas leak at 206 Springdale Lane, near Millersville, when the explosion occurred.

Blue Rock Fire Rescue Commissioner Duane Hagelgans said three UGI workers and a Lancaster Area Sewer Authority employee were working outside the home when it exploded.

He said fire crews "heroically" went in after the blast to rescue the victims.

UGI worker Richard A. Bouder, 54, was pronounced dead at the scene by Deputy Coroner Richard Graff, according to county coroner Dr. Stephen Diamantoni.

The three other workers were taken to Lancaster General Hospital. One UGI employee was in serious condition while the other two workers were listed as stable, according to Hagelgans.

In a statement released Sunday night, UGI officials said the two injured workers are expected to fully recover.

The statement continued, “The entire UGI family is deeply saddened by this tragic event. Our thoughts are with the family of our fellow employee who lost his life as well as our employees who were injured, and their families.”

“They were doing their investigation. That’s all we know at this point,” Steve Cook, director of business development for UGI, said. “Obviously, there was an explosion. We are conducting an investigation” into what happened.

A utility crew responded to the area after a passerby detected an odor of gas, according to Hagelgans.

UGI representatives arrived and evacuated a woman from the home. Fire crews were called to stand by at 12:23 p.m. and the blast occurred less than 10 minutes later.

Hagelgans said there was an initial “fireball” and then residual fire in the home which crews extinguished after pulling the victims from the debris.

Four surrounding homes also were damaged in the explosion and have been condemned, Hagelgans said.

The entire block was without gas service Sunday night and six to seven homes also were without electric.

“The last thing we want to do is turn any utility back on before we know that it’s safe,” Hagelgans said.

He said Sunday night that officials had not yet determined what caused the gas leak and susbsequent blast.

'It was mayhem'

Jeannine Hughes, who was surveying the damage from the yard behind the blasted house, identified herself as the homeowner.

Debris from the house littered lawns more than a block from the explosion.

Heavier chunks of debris, including pieces of the roof and walls and broken furniture, were spread far from the blast, even hanging from nearby trees. The windows and doors in the house next door were blasted from their frames.

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A neighbor who was in the street when the house exploded said it looked like a small mushroom cloud.

“It just exploded,” said Tracy Seiger, who lives a few houses down from the scene on Springdale Lane. “It was like a movie — the debris just flew up in the air.

“I started screaming, ‘oh my God, oh my God.’ We wanted to run — we wanted to run toward the explosion and we wanted to run away. Then a firefighter came running and told us to get back.

“It was mayhem.”

Barbara Hough Roda, the executive editor of LNP and LancasterOnline, was in the neighborhood Sunday and heard the blast.

“We heard it, we felt it,” she said. “Pictures fell off the wall.”

Many residents in the area are outside, trying to figure out what happened, Roda said.

“The neighborhood felt like it was going to blow,” she said. “It was horrible. It was worse than anything I've ever heard.”

Rob Heckman, who lives less than a block away on Scarborough Lane, said he was sitting in his living room when “the windows and walls buckled” from the explosion.

“It was an unbelievable event,” he said. “I was nervous at first that something in my house had exploded, it was so intense.”

Mark Smoker, who lives on Knollwood Road, parallel to Springdale, said the explosion was felt throughout the neighborhood and “caused some minor damage to some of the houses.”

A neighbor who lives several doors down from the explosion, who asked not to be identified, said the blast was so loud he thought something had landed on his roof.

A woman, a few doors down the street, was outside surveying the debris in her yard and described the scene as “unreal.”

Second natural gas blast in six years in Millersville area

While such explosions are rare, according to Hagelgans, Sunday’s blast was the second natural gas explosion in the Millersville area in the last six years.

In October 2011, a blast leveled The Framery Etc. business at 10 Manor Avenue in the borough. The explosion occurred after a construction crew struck an 8-inch gas line.

The building, along with several neighboring properties, had been evacuated about 90 minutes before the blast,which blew off the front of the building and toppled power lines.

No one was injured.

The business, which was destroyed, re-opened the following spring at the Wheatland Shopping Center on Columbia Avenue.

In May 2013, UGI agreed to pay a $200,000 civil penalty to the state PUC which alleged that the utility had failed to properly mark its underground facilities and to have procedures in place to accurately locate lines.

Despite agreeing to pay the penalty, UGI did not admit to violating any state or federal regulations in connection to the accident.