89-year-old man, 87-year-old woman killed in house explosion, fire: 'Complete devastation'

An 89-year-old man and an 87-year-old woman were killed when their house exploded and caught on fire in Pennsylvania, authorities said.

The victims were identified as David Mitchell Jr. and Helen Mitchell, the Allegheny County Medical Examiner's Office said.

The explosion in Crescent Township, just outside of Pittsburgh, was reported at 8:54 a.m. Tuesday, local officials said.

The home was completely leveled by the blast, and the fire was throughout the house's foundation and along the hillside, authorities said.

"We all felt and heard the explosion," Allegheny County Division Fire Chief Andrew Tomer said at a news conference. "You could feel it in your chest."

No injuries were reported, Tomer said.

"When the explosion happened, I thought either a truck hit our building or something happened within our factory," John Bundy, who works at a factory in the area, told ABC News. "We saw, like, a mushroom cloud explosion."

Bundy said he and his nephew "jumped in my truck and we drove to try to find the scene. And when we got there, we were along with two other gentlemen first on the scene that saw what was going on. And, we -- with caution -- ran up to the house."

Bundy said another man "ran right into the flames and was screaming and asking for survivors. And it was just really impressive to see."

"We did see a lady come out of her house with the windows were all blown out, and she was holding a baby," Bundy said. "She said her parents lived [at the house that exploded]. And we went to her right away because obviously, you know, she needed consoling. And, it was just a bad scene."

"It was complete devastation when we first arrived on scene," Tomer said.

"The whole lot was just completely leveled -- nothing remaining," Logan Barcia, Bundy's nephew, said.

At least two other homes were damaged, Tomer said.

The cause of the explosion has not been determined, officials said.

"There was natural gas on site from a private well. There was also propane on site from a private well," Tomer said.

ABC News' Chris Looft contributed to this report.