Waco, TX – The fire that killed a Waco man and injured his three grandchildren was caused by a natural gas explosion, officials said Tuesday.

The explosion killed Tommy Patton, 86, at a home at 1132 Faulkner Lane at about 11:35 p.m. April 16. Two of his grandchildren, girls ages 5 and 6, remained Tuesday in the burn unit at Parkland Hospital in Dallas, Waco Police spokesman Steve Anderson said. One of the girls remained in intensive care, while the other was in the less-serious acute care unit.

Waco Fire Lt. Charles Lindorfer said investigators had determined the deadly fire was the result of a natural gas explosion. Many neighbors told the Tribune-Herald they had heard a loud, “bomblike” explosion before seeing the fire.

Further details about the explosion’s cause were not released Tuesday,

Patton died from smoke inhalation and burns from the fire, according to a preliminary autopsy report.

An account has been set up for Patton’s grandchildren and family at Community Bank and Trust, a bank spokeswoman said.