Investigators are seeking the cause of a house fire in Northeast Philadelphia that killed a married couple and injured their daughter and son-in-law.

The blaze was reported at 11:58 p.m. Monday in the two-story rowhouse on the 10900 block of Modena Place, authorities said.

Arriving firefighters found heavy smoke and flames at the home, as well as two adult residents on the lawn.

After gaining entry, firefighters found the bodies of a 78-year-old man and his 68-year-old wife on the ground floor, police said.

The couple’s daughter and son-in-law, both 46, were taken to Jefferson-Torresdale Hospital, where they were reported to be in stable condition with unspecified injuries.

Officials have not released any names.

The fire was declared under control at 12:29 a.m. Tuesday.

Neighbors told NBC10 that the couple who died had health issues and that one of them relied on oxygen. Hours after the blaze, a firefighter carried two oxygen tanks out of the house.