Evansville, IN – Evansville — Investigators say undetected natural gas in a basement led to an explosion and fire that leveled an Evansville house and killed two people.

Josie Williams died early Sunday at Vanderbilt Hospital in Nashville, Tenn.

She had been burned severely in the Saturday blast, which killed the homeowner, 89-year-old Daisy Pauline Hardy.

The explosion also sent Vectren employee Mark Rexing to the burn unit of Wishard Memorial Hospital in Indianapolis.

Fire Department investigator Jesse Storey told the Evansville Courier & Press on Sunday evening that a gas leak occurred after city water department employees mistook the gas line to Hardy’s house for a water line.

Storey believes the gas rushed out of a broken plastic pipe and into a metal one that stopped short of the home’s basement. The metal pipe then allowed the gas to move through the ground toward the home’s basement.

The ground acted as a filter, Storey said, removing the odorant. Natural gas, which is odorless, has an odorant added to alert people to leaks.

Rexing made the repairs to the broken line, but the gas remained in the basement.

Smelling no gas, he tried to relight the pilot light on the water heater. As soon as he struck a match, the home exploded.