At least 39 migrants from Central and South America died after a fire broke out late on Monday at a migrant facility in the Mexican northern border city of Ciudad Juarez, the government’s National Migration Institute (INM) said on Tuesday.

In a statement, the INM said there were 68 adult men from Central and South America staying at the facility in the city opposite El Paso, Texas, and that 29 of them were also injured in the blaze and taken to four hospitals in the area.

A Reuters witness saw bodies lined up in body bags and confirmed that the fire, whose origins are under investigation, had been extinguished. Many of the migrants at the facility were Venezuelan, according to the Reuters witness.

The fire, one of the deadliest to hit the country in years, occurred as the U.S. and Mexico are battling to cope with record levels of border crossings at their shared frontier.

Recent weeks have seen a build-up of migrants in Mexican border cities as authorities attempt to process asylum requests using a new U.S. government app known as CBP One.

Many migrants feel the process is taking too long and earlier this month hundreds of mostly Venezuelan migrants got into a scuffle with U.S. officials at the border after their frustration welled up about securing asylum appointments.

In January, the Biden administration said it would expand Trump-era restrictions to rapidly expel Cuban, Nicaraguan and Haitian migrants caught illegally crossing the U.S.-Mexico border in an effort to contain the border flows.

At the same time, the United States said it would allow up to 30,000 people from those three countries plus Venezuela to enter the country by air each month.