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GLADWYNE, Pa. (CBS) — Police and fire officials are investigating a massive mansion explosion in Gladwyne.

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All occupants were able to get out of the house at 649 Dodds Lane and are fine, officials say.

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The house exploded around 8 p.m Sunday. The home was undergoing extensive renovations before the incident. Officials estimate that 75 percent of the 8,000-square foot residence was leveled in the blast.

Officials say the home is owned by Joseph and Donna Grasso. They were staying inside a carriage house on the property when the explosion happened and were not hurt.

“This house back in here, it blew out the front doors, it blew out windows, the house next to it, it blew out windows,” said Chief Chas McGarvey

Video from a doorbell camera nearby shows a flash, then a roar.

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When the 10-bedroom, five-bathroom house on Dodds Lane exploded, plywood and other debris were sent flying into the air with some of it landing in trees.

“I was in my driveway and I just heard the loudest sound I ever heard in my life. I had no idea what it was,” said Elizabeth Masoudina, who lives nearby.

From above, Chopper 3 captured the mangled mess of the home that sold for $3.4 million about 10 years ago.

The house was under extensive renovations and the owner spent nearly $1 million recently to renovate the residence, according to officials.

Neighbors say the place has been under construction for as long as they can remember.

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The explosion could be heard as far away as New Jersey.

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There is no word yet on what caused the explosion, but officials believe the blast was caused by a gas leak. An investigation is ongoing with help from the state fire marshal and the ATF.