Mexican prosecutors on Wednesday announced launching a homicide investigation into the recent deaths of 39 migrants in a detention center fire, accusing the people in charge of doing nothing to evacuate them.

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 locked inside.

An investigation was opened "for the crime of homicide and damage to property," though other possible crimes would also be considered, confirmed Sara Irene Herrerias, a prosecutor specializing in human rights.

"None of the public servants or the private security personnel took any action to open the door for the migrants who were inside," she told reporters.

Eight people had been identified as allegedly responsible for the failure following the fire that began late Monday, Mexican Security Minister Rosa Icela Rodriguez said at the same news conference. 

Those include two federal agents and a state immigration official, as well as five members of a private security company.

Prosecutors were seeking several arrest warrants, Herrerias said.

A migrant had been accused of starting the fire by others who were inside the detention center, she added, without giving details about the person.

Mexican President Andres Manuel Lopez Obrador earlier vowed that there would be "no impunity" over the tragedy in Ciudad Juarez across the border from El Paso, in the US state of Texas.

Those found to have been responsible for "causing this painful tragedy will be punished in conformity with the law," he told reporters.

Lopez Obrador on Tuesday said the migrants were believed to have started the fire themselves in a protest against deportations.

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 rapidly fills the building.

El Salvador, which said some of its citizens were seriously injured, demanded the people running the facility be punished since the video showed migrants "were left inside the cells without any chance of getting to safety."

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 dead and 27 injured included people from Guatemala, Honduras, Venezuela, El Salvador, Colombia, and Ecuador, Mexican authorities said.

A Honduran embassy official, Dimas Escobar, told AFP in Ciudad Juarez that some of the injured were "unrecognizable", making it hard to determine their nationalities.

Migrants left candles and flowers during a vigil outside the center, demanding better treatment by authorities.

Migrants also held protests in Mexico City and the country's south.

Following the tragic incident, 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," the Pope said.

United Nations chief Antonio Guterres called for a "thorough investigation" into the fire.

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