Honduras President Porfirio Lobo has pledged a "full and transparent" investigation after a fire at a jail killed more than 300 inmates.
Mr Lobo also suspended local and national prison officials while the inquiry into the "unacceptable" tragedy at the jail in Comayagua was conducted.
Many victims were burned or suffocated to death in their cells.
Officials fear the death toll could rise to more than 350, as dozens of inmates are still unaccounted for.
The authorities are trying to establish whether the blaze in the overcrowded prison was started deliberately by an inmate or was caused by an electrical fault.
Desperate for news, relatives and friends of prisoners later clashed with police as they tried to force their way into the prison compound.
Police responded by firing warning shots and tear gas to disperse the crowd.
'We will all die here!"
Mr Lobo promised to "find those responsible" for the disaster.
"It will be an independent investigation monitored by international observers," the president said.
The fire in Comayagua, about 100km (60 miles) north of the capital Tegucigalpa, broke out late on Tuesday night and took more than an hour to be brought under control.
Dozens of prisoners were trapped in their cells and were burned beyond recognition.
Comayagua firefighters' spokesman Josue Garcia said there were "hellish" scenes at the prison and that desperate inmates had rioted in a bid to escape the flames.
"We couldn't get them out because we didn't have the keys and couldn't find the guards who had them," he said.
One prisoner, who managed to escape, later told reporters that he first had heard "the screams of the [inmates] on fire and everyone just started fearing for their lives".
"The only thing that we were able to do was start breaking the roof apart so we could go out from above. We started ripping apart the ceiling above us."
Other survivors told investigators that one of the inmates started the fire by lighting fire to his bedding. They said he screamed "We will all die here!"
Prison service head, Daniel Orellana, confirmed that the investigators were looking into this version of events.
"We have two hypotheses. One is that a prisoner set fire to a mattress and the other one is that there was a short-circuit in the electrical system," he was quoted as saying by Reuters.
Honduran media reported that there had been a riot in the prison before the fire broke out.
Lucy Marder, who heads the forensic services in Comayagua, said that 356 people on the prison roster were unaccounted for on Wednesday.
"The majority could be dead, though others could have suffered burns, escaped or survived," Ms Marder said.
It was feared many inmates had fled.
Amid the confusion, relatives gathered outside the prison to try to get information.
"I'm looking for my brother. We don't know what's happened to him and they won't let us in," Arlen Gomez told Honduran radio.
Local hospitals are treating dozens of people for burns and other injuries.
Some of the injured have been taken to Tegucigalpa for treatment, among them 30 people with severe burns.
Firefighters said they had struggled to enter the prison because shots had been fired.
Prisons in Honduras, which has the world's highest murder rate, are often seriously overcrowded and hold many gang members.