FREEBORN — Fire officials confirmed Monday an uncapped sewage line caused the explosion at a house north of Freeborn on Friday that badly burned a man.

Freeborn Fire Chief Steve Siepp and a representative from the State Fire Marshal’s office investigated the explosion at 29462 660th Ave. Monday morning.

Siepp said they found that some sewer gas had backed into the house from the septic tank, and the gas sparked when Ralph William Yotter, 75, came into the house and turned on the light switch.

Yotter suffered burns to his face and body and remained in serious condition at Regions Hospital in St. Paul as of Monday afternoon.

Yotter and his wife, Patricia, had been mowing the grass around the house, and Patricia was standing outside during the explosion. According to authorities, the Yotters recently sold their property and were awaiting closing on the paperwork. They were not living there.

Patricia did not sustain burns but was treated and released from Mayo Clinic Health System in Albert Lea for other injuries.

The structure has been declared a total loss.