At least 51 inmates were killed and two dozen more injured early Tuesday after a fire broke out during a prison riot in southwestern Colombia, the national prisons agency said.

The tragedy occurred when rioting inmates set a fire at around 2:00 am to try to prevent police entering their enclosure at the prison in the city of Tulua, said Tito Castellanos, director of the National Penitentiary and Prison Institute (INPEC).

"Unfortunately 51 prisoners died and another 24 were injured," Justice Minister Wilson Ruiz told W Radio.

Six of the injured remained "in the intensive care unit in Tulua," he added.

Castellanos had earlier given the "riot" death toll as 49 with another 30, including six prison guards, "injured and affected by the blaze and the smoke."

The prison, which holds more than 1,200 inmates, was surrounded by police and soldiers.

By late morning, no bodies had been removed from the prison.

"By setting mattresses alight, they had not gauged what the consequences could be and unfortunately this happened," Castellanos told Radio RCN.

He said the blaze had been brought under control by firefighters.

Outside the prison, dozens of family members gathered hoping for information on their loved ones.

A prison official gave an initial list of survivors to those waiting.

"I don't know anything, INPEC won't let us in," a tearful Maria Eugenia Rojas, whose son Luis Miguel Rojas is an inmate in the pavilion where the riot happened, told Caracol television.

Lorena, who did not give her surname, told the El Tiempo newspaper that she had spoken to her inmate partner at dawn.

"It seems illogical to me that people enclosed in a building would have set mattresses alight knowing that they could have been burned," she said.

It could 'have been worse

Authorities had initially said they were investigating whether the incident occurred as part of an escape attempt but later said it was a riot.

"This situation was provoked by a fight that broke out between prisoners. One of the inmates set fire -- he was angry, upset -- to a mattress, which provoked the blaze," said Ruiz.

There were 180 inmates in the prison section affected by fire.

Castellanos praised the efforts of prison guards to control the blaze and help prisoners to safety.

He said that without their intervention "the result would have been worse."

Forensics experts are trying to identify the victims.

Outgoing President Ivan Duque sent a tweet offering his solidarity with relatives of the victims.

"We regret the events that occurred in the prison in Tulua, Valle del Cauca," Duque said.

"I have given instructions to clarify this terrible situation. My solidarity is with the families of the victims."

President-elect Gustavo Petro also expressed his sympathies and said on Twitter that there needed to be "a complete rethinking of prison policy" that takes into account "prisoner dignity."

"The Colombian state has viewed prison as a space for revenge and not for rehabilitation," added Petro, who won an election runoff earlier this month and will replace Duque on August 7.

He also made reference to a riot at the La Modelo prison in Bogota in 2002 that left 23 inmates dead.

Fatal prison riots are not uncommon in Latin America. In Colombia's neighbor Ecuador, nearly 400 prisoners have been killed in six riots since early 2021.

Colombia's prison system has a capacity for 97,000 inmates but is overpopulated by some 16,000, according to INPEC.

"So far there are 49 dead," said a spokesperson for the National Penitentiary and Prison Institute, adding that the toll from the city of Tulua was preliminary and "may change."

The tragedy occurred during an escape attempt followed by a fire, Caracol Radio quoted authorities as saying.

According to that report, more than 40 people have been injured.

Outgoing President Ivan Duque sent a tweet offering his solidarity with relatives of the victims.

He did not provide a death toll.

"We regret the events that occurred in the prison in Tulua, Valle del Cauca," Duque said.

"I have given instructions to clarify this terrible situation. My solidarity is with the families of the victims."

Fatal prison riots are not uncommon in Latin America. In Colombia's neighbor Ecuador, nearly 400 prisoners have been killed in six riots since early 2021.