MANVILLE, NJ (CBSNewYork) — Officials still don’t know what caused pressure to build up in a boiler that exploded at a home in Manville that sent two PSE&G workers to the hospital.

1010 WINS’ Glenn Schuck reports: Explosion Not Caused By Gas

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The explosion happened Saturday afternoon at a home on Huff Avenue in Manville. Two PSE&G workers had been called to the home after homeowners reported the boiler was getting hot.

PSE&G supervisor Mike Schmid said as they workers were heading down into the basement, the boiler exploded.

“There was no gas involved whatsoever. It was all from the pressure built up inside the hot water boiler that exploded. We don’t know exactly what made the explosion occur,” said Schmid.

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The explosion caused the stairs to collapse underneath them. The two workers were flown to a nearby hospital. Manville Emergency Management Director Ken Otrimski said it appeared the workers suffered burns.

WCBS 880’s Alex Silverman reports Officials Don’t Know Why The Boiler Overheated

The homeowner was also hurt, but not seriously. The homeowner was taken to the hospital, treated and released.

The home had suffered extensive flooding after Irene as did large portions of Manville, but Schmid says they still don’t know what exactly made the pressure build up inside the boiler.

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The cause of the explosion is still under investigation.