Debris from an explosion at the Escambia County Jail is scattered at the entrance to the facility, Thursday, May 1, 2014, in Pensacola, Fla. Two inmates were killed and more than 100 others injured in the explosion according to an Escambia County spokeswoman. (AP Photo/John Raoux)

May 1 (Reuters) - Two inmates were killed and roughly 150 prisoners and guards injured in an apparent gas explosion at a jail in northwest Florida late on Wednesday, and county officials said many had been treated and released by Thursday morning.

The blast partially leveled the four-story Escambia County Jail's central booking facility in Pensacola, which held roughly 600 inmates, at about 11 p.m., county spokeswoman Kathleen Castro said. No escapes were reported.

"The building is still standing, it's just unstable and partially collapsed," Castro said, describing the incident as an "apparent gas explosion."

"We have reports people heard an explosion and smelled gas. There was no fire," she said, adding that the blast may have been related to severe storms that have hit the southern United States, damaging buildings and infrastructure.

"The facility did receive extensive flooding as a result of the rains yesterday," Castro said. Flooding, she said, "would seem to be a causal relationship, but we can't be sure."

The state fire marshal and agents with the Bureau of Alcohol, Tobacco, Firearms and Explosives were investigating at the scene, she said.

She said two inmates were killed and between 100 and 150 of those present were injured, adding it was unclear how the inmates died or the breakdown of injured inmates and guards.

Calls to four area hospitals showed 151 people were transported with non-life threatening injuries, at least one of them a corrections officer. Roughly 80 had been treated and released by Thursday morning.

A statement on the Escambia County website made no mention of gas, saying only it was an "apparent explosion" after earlier reporting it was "an apparent gas explosion".

Castro described a frenetic scene where officials were scrambling to get people out of the building, provide medical care, and working to make sure inmates were detained and routed to other facilities. The search and rescue operation was ongoing, though the building has been secured.

The facility holds about 400 men and 200 women. Injured prisoners were being transported to the hospital, with those uninjured being sent to other detention centers in Escambia County and neighboring Santa Rosa County, Castro said.

About 100 inmates were being transferred to the Santa Rosa County Sheriff's Office jail, though the exact number was not known, office spokesman Rich Aloy said. (Reporting by Eric M. Johnson in Seattle, additional reporting by Curtis Skinner in New York,; Editing by Alison Williams and Nick Zieminski)