(AP) - Authorities say an explosion that killed a New Jersey couple and leveled their home last week was caused by a gas build-up of some kind.

But the Gloucester County Fire Marshal's Office says it couldn't pinpoint the source of the gas leak or say what sparked the blast in Newfield on Saturday. The agency issued its finding Monday, listing the nature of the explosion as "undetermined."

An office spokeswoman said "numerous sources of ignition" set off the explosion that killed 73-year-old John Paladino and his 72-year-old wife, Carole.

Neighbors have said the couple had a new stove delivered the day before the explosion occurred. But the office's finding didn't mention the stove in its determination.

The Gloucester County Prosecutor's Office declined comment Monday on its ongoing investigation into the blast.