(CNN) -- A fatal explosion at the Escambia County Jail last week was caused by a natural gas release into the facility, the Florida state fire marshal said Friday.
Two inmates were killed in the explosion and 155 other inmates and jail staff were injured.
The explosion in the medium-security facility happened near the jail's booking area, said county spokeswoman Kathleen Castro.
It appeared the ceiling and part of a wall had collapsed, she said.
About 600 inmates were in the jail at the time, Castro said.
"It's pretty much complete destruction inside this facility. It was a huge explosion," Sheriff David Morgan said at the time. He added that the building would likely be a total loss.
The cause of the explosion, which took place April 30 following torrential rain and heavy flooding in the area, was determined following an investigation by the Florida State Fire Marshal's Office and the Bureau of Alcohol, Tobacco, Firearms and Explosives, according to the release.
"The on-scene phase of our investigation may be complete, but there is still much to be learned," State Fire Marshal Jeff Atwater said in a statement. "Our investigators will continue to work day and night with the ATF and the State Attorney's Office to uncover all of the answers victims and their families deserve to know."
The State Fire Marshal's Office declined to answer any additional questions from CNN over the phone.
CNN's Marlena Baldacci contributed to this report.