The blast late Wednesday created a chaotic scene as injured inmates were bused to hospitals and others were taken to nearby jails because the crippled building had to be evacuated.
"The explosion shook us so hard it was like we were in an earthquake," Monique Barnes, an inmate who said she was knocked off her fourth-floor bunk, told The Associated Press by phone. "It was like a movie, a horrible, horrible movie."
Pieces of glass and brick were strewn about on the ground outside the jail and the front of the building appeared bowed, with cracks throughout.
Barnes, who spoke to AP after she was taken to another jail, said she and other inmates complained of smelling gas ahead of the blast, and some reported headaches.
At a news conference, Escambia County Sheriff David Morgan wouldn't comment on whether inmates complained about gas. He said three inmates were unaccounted for and the jail was almost completely destroyed.
Authorities blocked off roads leading to the detention center and relatives and attorneys for the inmates stood behind police tape, trying to figure out where loved ones had been taken and who was injured and killed.
About 600 inmates - 200 men and 400 women - were in the building at the time of the explosion. Barnes said during the evacuation, hundreds of inmates and corrections officers had to use one stairwell, "everyone pushing and bleeding."
County spokeswoman Kathleen Castro said authorities did not yet know the extent of the injuries, but local hospitals said some inmates had already been released. The sheriff said a corrections officer was seriously injured.
The names of the two inmates killed in the explosion weren't immediately released.
The Pensacola area was drenched by rains and severely flooded Tuesday and Wednesday as part of a large storm system making its way across the U.S. Castro said the building was running on generator power. Barnes said the toilets weren't working, so they had to use plastic trash bags.
Officials don't know yet whether the flooding and explosion were related. The fire marshal would ultimately determine the cause.
A couple of blocks from the jail, Ellis Robinson and his family awoke to a loud noise, their home rattling.
"It shook the whole house," he said. "I got up, the dog started barking, people were running up there."
He said he spent the night observing the chaos as inmates were loaded into buses.
Defense attorney Gene Mitchell stood behind the police tape Thursday, reviewing dozens of text messages from clients' relatives.
"I have over 20 clients in there," he said. "I've had dozens of calls. Every other call is a family member wanting to know what has happened to a loved one."
He said he hasn't been able to get much information about the inmates. Castro said officials were having trouble notifying families because it wasn't safe to enter the jail to access computers and paper records.
By midday Thursday, there were dozens of firefighters in hard hats going in and out of the building.
At one point during the sheriff's news conference, a woman whose son was in the jail interrupted, demanding to know what happened to her son. Sheila Travis said she had called hospitals and couldn't get any information. The sheriff said officials were doing all they could.
Escambia County took over the jail, its operations and its 400 employees from the sheriff's office on Oct. 1 after a five-year federal investigation of the facility. According to the Pensacola News Journal, the investigation found that inadequate management of the jail had led to violations of the inmates' rights.
Problems included a low number of guards overseeing the inmates, which led to high levels of violence among the inmates, inadequate mental health care and a decades-long practice of segregating inmates by race. Morgan has been sheriff, an elected position, since 2009.
John Mone and John Raoux of The Associated Press contributed to this report in Pensacola. Associated Press writer Freida Frisaro in Miami also contributed.