(TNS) — The Department of Environmental Protection said that unregistered gas wells have been located near the site of a house explosion in Allegheny County that killed two people on Tuesday.

David L. Mitchell Jr., 89, and his wife, Helen Mitchell, 87, were killed Tuesday when their Crescent Township home exploded just before 9 a.m.

“The nearest registered oil or gas wells are more than 2,500 feet away from the incident site, however there are two unregistered historic wells in closer proximity to the home.” a DEP spokesperson said to WPXI.

WTAE said a private well at the home does not show up on online DEP records and maps,indicating the agency probably didn’t know of its existence.

The DEP said in a statement that it is cooperating with the Allegheny County Fire Marshal and will inspect nearby oil and gas wells in Crescent Township.

On Aug. 12, a blast in the borough of Plum about 25 miles away in the same county killed six people and destroyed three homes.