PLUM,Esthen Pa. (AP) — The co-owner of a home that exploded in western Pennsylvania last weekend has died from injuries he suffered in the blast, which also killed his wife and four other people.

Paul Oravitz, 56, who had severe burns over most of his body, died Wednesday in a Pittsburgh hospital, four days after the explosion in Plum. The town is about 20 miles (32 kilometers) east of Pittsburgh.

The cause of the blast — which destroyed three structures and damaged at least a dozen others — remains under investigation, but officials have said Oravitz and his wife, Heather, were having issues with their hot water tank. The Allegheny County fire marshal’s office is leading the investigation, along with local law enforcement.

The explosion occurred shortly before 10:30 a.m. Saturday. Heather Oravitz, 51, who was Plum’s community development director, was killed in the blast along with Plum Borough Manager Michael Thomas, 57, and three others who lived in the neighborhood: Kevin Sebunia, 55; Casey Clontz, 38; and Clontz’s 12-year-old son, Keegan.

The development is on abandoned mine land surrounded by shallow oil and gas wells, some of which have been abandoned. Two wells that are still producing gas are within about 1000 feet (305 meters) of the home that exploded and a pipeline runs behind the development, but none of those structures have been identified as having been involved in the blast, the newspaper reported.

Michael Huwar, president of Peoples Gas, has said official checks by the company indicated that “our system was operating as designed.”

A company spokesperson said Wednesday that it had completed additional system testing with the Fire Marshal’s office and the state Public Utility Commission, meaning it can now begin restoring gas service. Company technicians will be going door to door to conduct a safety check and relight customers’ appliances, the spokesperson said.

A county spokesperson had said Tuesday that electrical service was restored by Sunday afternoon to all homes other than the three that were destroyed, and gas service had been restored to all homes except the loop where the blast occurred and two spur roads.