Fort Worth officials have not yet revealed what caused an explosion at a power substation that led to a large fire.

Investigators say the substation holds about 30,000 gallons of oil. It's unclear how much of it has already burned off.

The fire that sparked Wednesday night at a Fort Worth power substation is out and crews have left the scene, officials said Thursday morning. The substation erupted in flames hours before a winter storm hit North Texas with a forecast for inches of snow and sleet, officials with the Fire Department and Oncor Electric Delivery said.