Ciudad Juárez (Mexico) (AFP) - A fire started by migrants in an apparent protest against deportations killed at least 40 people at a Mexican immigration detention center near the US border, authorities said Tuesday, prompting demands for justice.

The blaze broke out late Monday at the National Migration Institute (INM) facility in Ciudad Juarez, prompting the mobilization of firefighters and dozens of ambulances.

The migrants were believed to have lit the fire as a demonstration because they feared they would be deported, President Andres Manuel Lopez Obrador said.

“They put mats at the door of the shelter and set them on fire as a protest, and did not imagine that it would cause this terrible tragedy,” he told reporters.

United Nations High Commissioner for Refugees Filippo Grandi expressed solidarity with relatives of the victims, and appealed to countries in the region “to deal in a humane, just, effective manner with growing population flows through the Americas.”

Anger grew outside the detention facility, with relatives chanting demands for justice near a makeshift shrine dedicated to the victims.

“Every migrant has the right to be safe, to be protected,” said Fran Martin Perez, from Venezuela.

“Because we’re not criminals,” he added.

Amnesty International said the fire was “a consequence of the restrictive and cruel immigration policies” of Mexico and the United States.

“These devastating events lay bare a truly inhumane system of immigration enforcement. How is it possible that the Mexican authorities left human beings locked up with no way to escape the fire?” said the rights group’s Americas director, Erika Guevara-Rosas.

- Video raises questions -

Video surveillance footage, broadcast by several media and authenticated by a government minister, appeared to show guards at the detention center leaving as flames engulfed a cell with migrants trapped inside.

“We had this video since last night. But in order not to hinder the investigations, out of respect for the victims, we must be careful,” Interior Minister Adan Augusto Lopez said about the images.

A Venezuelan woman who gave her name as Viangly waited desperately for information about her 27-year-old husband.

“A family member can die and they don’t tell you he’s dead,” she said, her voice cracking.

At least 40 immigrants were killed and 28 were injured, according to the INM, which said the center housed 68 adult males from Central and South America.

The dead and injured included people from Guatemala, Honduras, Venezuela, El Salvador, Colombia and Ecuador, Mexican authorities said.

Guatemalan Foreign Minister Mario Bucaro told reporters that 28 citizens of his country were killed.

UN Secretary-General Antonio Guterres called for a “thorough investigation” into the fire.

He pledged “to continue working with the authorities of countries where mixed movements of people occur to establish safer, more regulated, and organized migration pathways,” a spokesman said.

- ‘Unnecessary danger’ -

Ciudad Juarez, which neighbors El Paso, Texas, is one of the border towns where numerous undocumented migrants seeking refuge in the United States remain stranded.

Fed up with waiting at the border, hundreds of the migrants attempted to storm an international bridge on March 13 but were blocked by US agents.

“Deteriorating conditions in migrant facilities along the border mean vulnerable asylum seekers are in unnecessary danger,” the International Rescue Committee humanitarian organization said.

“Stronger systems along Mexico’s migration corridors are critical to provide asylum seekers with the protection they need,” it added.

The US ambassador to Mexico, Ken Salazar, said the tragedy was “a reminder to the governments of the region of the importance of fixing a broken migration system and the risks of irregular migration.”

President Joe Biden’s administration has been hoping to stem the record tide of migrants and asylum seekers undertaking often dangerous journeys organized by human smugglers to get to the United States.

About 200,000 people try to cross the border from Mexico into the United States each month, most of them fleeing poverty and violence in Central and South America.

According to the International Organization for Migration, more than 7,600 migrants have died or disappeared in transit in the Americas since 2014.

Of those, around 4,400 people perished or went missing on the US-Mexican border crossing route, according to the UN agency.