Mexican prosecutors said Friday that they had arrested a migrant accused of starting a fire that killed 39 people at an immigration detention center near the US border.
Three immigration officials and a private security guard have also been detained as part of a homicide investigation into the blaze that started on Monday night.
An arrest warrant was outstanding for another guard wanted in connection with the tragedy, Sara Irene Herrerias, a prosecutor specializing in human rights, told a news conference.
She did not identify the migrant accused of starting the fire in a cell where he was being held with 67 other men, apparently in a protest against deportations.
According to the authorities, the deceased were 18 Guatemalans, seven Salvadorans, seven Venezuelans, six Hondurans and one Colombian.
The injured were 10 Guatemalans, eight Hondurans, five Salvadorans and five Venezuelans.