MEXICO CITY — A fire in a dormitory at a Mexican immigration detention center near the US border killed more than three dozen migrants, according to a government agency, in one of the country's deadliest incidents at an immigration lockup.

Rows of bodies were laid out outside the facility in Ciudad Juarez, which is across the border from El Paso, Texas, and a major crossing point for migrants, hours after the fire broke out late Monday.

Ambulances, firefighters, and morgue vans swarmed the scene.

According to the National Immigration Institute, 39 people died and 29 were injured and are in "delicate-serious" condition. The facility was holding 68 men from Central and South America at the time of the fire, according to the agency.

It was the deadliest incident in recent memory inside a Mexican immigration facility. The cause of the fire is being investigated by authorities, and the government's National Human Rights Commission has been called in to assist the migrants.

Tensions between authorities and migrants appear to have been high in recent weeks in Ciudad Juarez, where shelters are full of people waiting for opportunities to cross into the United States or who have requested asylum and are waiting for the process to be completed.

More than 30 migrant shelters and other advocacy organizations published an open letter on March 9 complaining about the city's criminalization of migrants and asylum seekers.

It accused authorities of abusing migrants and using excessive force in rounding them up, claiming that municipal police were questioning people on the street about their immigration status without reason.

The high level of frustration in Ciudad Juarez was evident earlier this month when hundreds of mostly Venezuelan migrants tried to force their way across one of the international bridges to El Paso, based on false rumors that the US would allow them to enter the country. Their attempts were thwarted by US authorities.

The national immigration agency stated on Tuesday that it "energetically rejects the actions that led to this tragedy," but provided no further details.

The agency has struggled with overcrowding in its facilities in recent years, as Mexico has increased efforts to stem the flow of migration to the US border under pressure from the American government. Protests and riots have occurred in the country's immigration detention facilities on occasion.

In October, mostly Venezuelan migrants rioted inside a Tijuana immigration center that had to be controlled by police and National Guard troops. Hundreds of migrants rioted in Mexico's largest detention center in the southern city of Tapachula, near the Guatemalan border, in November. Nobody was killed in either incident.