Mexico's president on Wednesday vowed there would be "no impunity" over the deaths of 38 migrants in a fire at a detention center, as relatives waited desperately for news about the victims.
Authorities faced mounting scrutiny of their handling of the disaster after video surveillance footage appeared to show guards leaving as flames engulfed a cell with migrants trapped inside.
"We will not hide anything and there will be no impunity," President Andres Manuel Lopez Obrador told reporters after the blaze at a detention center in Ciudad Juarez near the US border late Monday.
Those found to have been responsible for "causing this painful tragedy will be punished in conformity with the law," he said.
In the video, whose authenticity was confirmed by the government, three guards seem to hurry away leaving migrants in their cell as flames spread and smoke fills the building.
"How is it possible that the Mexican authorities left human beings locked up with no way to escape the fire?" said Amnesty International's Americas director, Erika Guevara-Rosas.
The fire was "a consequence of the restrictive and cruel immigration policies" of Mexico and the United States, the rights group said.
Lopez Obrador said Tuesday that the migrants were believed to have started the fire themselves in a protest against deportations.
"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 said.
- 'We want to know' -
Dozens of migrants spent the night outside the National Migration Institute (INM) facility in Ciudad Juarez waiting for information about their relatives and friends.
The government had not yet identified those who lost their lives or the conditions of the 28 injured.
The group included people from Guatemala, Honduras, Venezuela, El Salvador, Colombia and Ecuador, Mexican authorities said.
"We want to know if they were in there or not," said Venezuelan Gilbert Zabaleta, who was looking for two friends.
Migrants left candles and flowers during a vigil outside the detention center, demanding better treatment by the authorities.
"You know what angers me? You arrive here after battling so hard in life," said 22-year-old Embeer Gutierrez, also from Venezuela.
Condolences poured in from abroad, including from Pope Francis.
"Let us pray for the migrants who died in a tragic fire in Ciudad Juarez, Mexico, so that the Lord receives them in his kingdom and consoles their families," he said.
United Nations Secretary-General Antonio Guterres called for a "thorough investigation" into the fire.
UN High Commissioner for Refugees Filippo Grandi appealed to countries in the region "to deal in a humane, just, effective manner with growing population flows through the Americas."
US 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, about 4,400 people perished or went missing on the US-Mexican border crossing route, according to the UN agency.
By Jose Osorio