An explosion at a dairy farm in the Texas Panhandle that critically injured one person and killed an estimated 18,000 head of cattle is the deadliest barn fire recorded since the Animal Welfare Institute began tracking the fires.

Castro County Sheriff Salvador Rivera has says the Monday fire and explosion at Southfork Dairy Farm near Dimmitt was likely caused by overheated equipment and would be investigated by state fire marshals.

A spokesperson for the state insurance department, which oversees the fire marshals’ office, said only that the fire is under investigation.

Dimmitt is about 80 kilometers southwest of Amarillo and 50 miles east of the New Mexico border.