MEXICO CITY (AP) — Mexican prosecutors said Friday they have arrested three more officials of the country's immigration agency for a fire at a detention center last month that killed 40 migrants.

Among those arrested were the local head of supplies for the immigration agency and an official of the Grupo Beta migrant protection service, the the Attorney General's Office said in a statement.

The director of agency for the northern border state of Chihuahua has been ordered to appear in court, but has not been arrested. The fire occurred March 27 in the border city of Ciudad Juarez, after a migrant allegedly set fire to foam mattresses to protest a supposed transfer.

The immigration agency's top national official, Francisco Garduño, is scheduled to make a court appearance April 21. At that point prosecutors will make their formal accusations and present evidence.

Prosecutors had announced Tuesday that Garduño would face unspecified criminal charges in the case.

President Andrés Manuel López Obrador, who has known Garduño for years and asked him to take the job in 2019 when then U.S. President Donald Trump was pressuring Mexico to reduce migration, said Wednesday that Garduño would stay in his job.

Federal prosecutors has said Garduño was remiss in not preventing the disaster in Ciudad Juarez despite earlier indications of problems at his agency's detention centers. Prosecutors said government audits had found "a pattern of irresponsibility and repeated omissions" in the immigration institute.

The fire in Ciudad Juarez, across the border from El Paso, quickly filled the facility with smoke; no one let the migrants out.

Three Mexican immigration officials, a guard and a Venezuelan migrant accused of starting the blaze are already in custody facing homicide charges.