By Mike McDonald

COMAYAGUA, Honduras (Reuters) - Honduras came under international pressure on Friday to fix its broken prison system and allow an independent inquiry into a jailhouse blaze this week that killed more than 350 inmates, many burned alive in their cells.

The blaze, the third major prison fire in Honduras in the last decade, has ramped up scrutiny of the Central American nation's corrupt judicial system. Almost half the inmates in its overcrowded jails have not been convicted and are awaiting trial, according to data from the Supreme Court of Honduras.

The United Nations said an independent investigation should look at whether conditions in the prison in Comayagua, about 47 miles north of the capital Tegucigalpa, contributed to the massive loss of life in Tuesday night's inferno.

One woman outside the prison said her uncle, 42-year-old Jose Donaire, had so far spent eight months in custody awaiting trial for stabbing a dog that attacked him.

"The dog is alive and my uncle is inside," said Belkis Donaire, 27, who said Jose had knifed the "large, vicious" black pitbull in the leg when it came after him.

"What kind of justice is this? We're lower than a dog. Put the damned dog on trial," said Donaire.

Prison guards used cell phones to take pictures of surviving inmates to show them to relatives who turned up asking to see their loved ones. But some were still left without answers.

"This is total chaos. Nobody knows anything," said Alba Arias, who came looking for her nephew Elmer Mejia, who she said had been awaiting trial for two years without being charged.

"They tell me that he is not inside, and he's not in the morgue. I don't know where he is," the 52-year-old Arias said.

Many victims were so badly burned their bodies were fused together in the fire, which destroyed about a third of the prison complex. Honduran authorities said DNA and dental records would be needed to identify some remains.

The Honduran government has so far confirmed 356 deaths. One man died of his injuries on Friday, a spokesman said.

Elimara Lavaire, a nurse with Honduras' Center for Prevention and Treatment of Torture Victims and Families, said prison reform in the nation was long overdue.

"Whatever the story is, the state is responsible," she said. "If it was because of the keys, who had the keys? If it was a fight, who was responsible for stopping it?"

DROPPED KEYS

The chief of police intelligence said the fire broke out during a fight between two inmates over a mattress. But other sources provided different explanations for the blaze, including a botched jailbreak and an electrical malfunction.

One of the prison guards told Reuters that keys to the cells had been locked in a safe for which special permission was needed, which delayed the opening of doors.

Survivor Carlos Rapalo, 50, who has served 17 years of a 25-year sentence for murder, said many prisoners were saved by a fellow inmate who picked up keys that a guard had dropped on the ground, and opened up the cells one by one.

The prisoner, a nurse by trade, was sleeping in the medical station on Tuesday night and not in his cell.

"If it was not for him, there would have been many more deaths," said Rapalo.

In Tegucigalpa, officials moved about 1,000 friends and relatives of victims from tents outside the morgue to a nearby camp, where many face a lengthy wait for the release of bodies.

Reina Hernandez, 29, lost two of her brothers to the blaze. The younger one, Carlos, was just 18. He was serving an eight-year sentence for murder when he was 14.

"My mother's crying now, she's really sad because she asked for him to be brought to this prison so she could visit him," she said. "She never thought that trying to get my little brother close meant he was going to die."

Forensic teams, including experts from Mexico, Chile and El Salvador, had identified 16 of the charred bodies on Friday and were still working on others, a government spokesman said.

(Additional reporting by Gustavo Palencia in Tegucigalpa; Writing by Krista Hughes and Dave Graham; Editing by Will Dunham)