Columbus, OH – Investigators say a natural gas leak contributed to the home explosion in Ohio that killed a 54-year-old woman, but the cause of the leak is still unknown.

In a statement Wednesday, Columbia Gas says they are confident their main lines and service lines did not contribute to the explosion.

Emergency responders received several calls from neighbors around 4 a.m. Monday after the explosion in southeastern Columbus.

Shelly Williams was pulled from the debris and her longtime boyfriend, 59-year-old Stewart Bell, was thrown from the home. Williams later died from her injuries. Their family dog survived.

Bell tells The Columbus Dispatch he smelled gas in the area last week, but he didn’t call because there was no smell inside the house.