COMAYAGUA, Honduras -- A fire that broke out in an overcrowded Honduran prison left as many as 350 inmates dead Wednesday as investigators pulled one body after another from the smoldering facility.

The fire, which started at 10:50 p.m. Tuesday at the Comayagua National Penitentiary, took firefighters three hours to douse. It may have been sparked by an inmate setting a mattress afire or by a short circuit, although its cause is yet unknown.

Guards fired their guns repeatedly to keep screaming trapped inmates from escaping.

“It is a day of deep pain for Honduras,” President Porfirio Lobo said in a brief televised address. He continued, “We will conduct an investigation to determine what provoked this lamentable and unacceptable tragedy and find those responsible,” Lobo said.

The death toll climbed throughout the day. At noon, Security Minister Pompeyo Bonilla said he thought that “more than 300” were dead. National Prison Director Danilo Orellana later told Honduran media that the toll had surpassed 350. At least one woman who was in the prison illegally was said to be among the fatalities.

Hundreds of other prisoners were burned in the blaze or injured when they broke through a roof and jumped to safety, hospital officials said.

Inside the burnt-out prison late Wednesday, inmates described awaking to the smell of smoke and the screams of friends in nearby buildings.

“I woke up and the first thing I saw was the guys from the building across from me getting burned alive,” said Francisco Martinez, 22, who’s serving a kidnapping sentence. “People were screaming for the keys to get the guards to unlock the doors.”

In one building, which housed between 75 and 100 inmates, the calcified bodies of about a dozen men were crowded around bathroom sinks. “They were trying to climb up, escape through the roof,” said German Enamorador, a human rights prosecutor who is investigating the fire. “Some took shelter in the tubs of water, which began to boil.”

Enamorador said there were 12 guards watching over the inmates in the low-security prison. One inmate blamed the government for the fire.

“Yesterday, some men who were here for stealing a cellphone died,” said Carlos Alberto, 35, who’s serving a sentence for drug trafficking. “There were people who already completed their sentences and still hadn’t been released. This is a complete abandonment by the authorities.”

Bonilla said the fire underscored “the dramatic situation in terms of security” that afflicts the Central American nation, which is on a major narcotics corridor and has been overrun by organized crime.

Anguished relatives banged on the gates and threw rocks at riot police and soldiers who were blocking access to the prison in Comayagua, a city about 55 miles north of Tegucigalpa, the capital. Police responded with tear gas. Gunfire rang out.

Riot police also closed off all public access to the morgue in Tegucigalpa where bodies were taken as relatives clamored for information about the identities of the victims.

In South Florida, Honduran advocates began receiving calls as early as 9 a.m. from anxious relatives of those who might have been housed at the prison.

Francisco Portillo said his group, Organizacion Hondurena Francisco Morazan, is offering help to those with temporary immigration status wishing to travel to Honduras to be with relatives. He said the group will help with filling out the necessary paperwork to allow those who travel back into the United States.