An explosion at a dairy farm has left one person in critically injured and caused a fire that killed an estimated 18,000 cattle, reports say.

The Castro County Sheriff’s Office says in a news release that a female worker at Southfork Dairy Farms was trapped inside a building after the explosion and fire Monday. Firefighters were able to rescue the woman, who was flown to UMC Hospital in Lubbock. KFDA Channel 10 reports the woman was in critical condition.

KFDA reports the cattle were in a holding area before being brought in for milking when the fire occurred. Very few cows in the holding area survived the fire, officials say.

The Animal Welfare Institute says that if the death estimate is correct, the fire is the deadliest involving cattle since the agency began tracking barn fires in 2013. (An earlier version of this story incorrectly reported that it was the deadliest fire involving cattle in Texas history.)

The cause of the fire remains under investigation, but Castro Sheriff Salvador Rivera tells Everything Lubbock that machinery at the dairy farm might have ignited methane gas buildup.