The house explosion that killed a Gloucester County couple last week was caused by natural gas, authorities said Friday, but investigators were unable to pinpoint the precise source of ignition.

The Fire Marshal's Office listed the origin of the blast that killed John and Carole Paladino as "undetermined," saying it found multiple possible sources of ignition. John Paladino, 73, and his wife, Carole, 72, died early last Saturday after a blast ripped through their home and pierced the morning calm of their Newfield neighborhood, sending debris flying for blocks and damaging nearby houses.

On Friday, the Medical Examiner's Office said Carole Paladino died of multiple blunt trauma and John Paladino succumbed to thermal injuries. Both deaths were ruled accidental. Authorities said there was no evidence of foul play in the explosion, which reduced the house on the 300 block of Oakwood Drive to rubble in what neighbors described as a "huge ball of fire."

As shaken residents gathered near the debris-strewed site where the house once stood, one said the couple had a stove delivered the previous day. The fire marshal's findings made no reference to the appliance.

John Paladino had served as president of the Newfield school board, friends said, and he worked part-time at the DeMarco-Luisi Funeral Home in Vineland, N.J. Carole Paladino was a retired school nurse who worked in Millville schools. According to the Vineland Daily Journal, Carole received a distinguished service award from the New Jersey State School Nurses Association in 2008. The couple had been married for 50 years.