The deaths of 39 migrants in a fire at a Mexican detention center are being investigated as suspected homicides, a prosecutor said Wednesday, accusing those in charge of doing nothing to evacuate the victims.

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

"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, Security Minister Rosa Icela Rodriguez said at the same news conference.

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

Prosecutors have already requested several arrest warrants, Herrerias said.

Mexican President Andres Manuel Lopez Obrador earlier vowed there would be "no impunity" over the tragedy in Ciudad Juarez near the US border.

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.

Rodriguez said the death toll had risen to 39, up from 38 previously, with 27 injured.