Reuters / Pool

Migrants detained at the McAllen Border Patrol Station.
The US border control agency has halted intake at a migrant holding facility in Texas after an outbreak of a "flu-related illness." The closure comes just one day after a 16-year-old detainee died in custody.

The Customs and Border Protection (CBP) agency said it would temporarily suspend operations at its primary migrant facility in McAllen, Texas, citing an unknown virus.

"To avoid the spread of illness" the agency has "temporarily suspended intake operations" at the McAllen facility, CBP said in a statement Tuesday, adding that medical staff had "identified a large number of subjects in custody with high fevers whom are also displaying signs of a flu-related illness."

New arrestees will be diverted to other holding centers "until this situation is resolved," the statement said.

Sixteen-year-old Guatemalan migrant Carlos Hernandez was found unresponsive on Monday at a nearby holding center after spending six days at the McAllen facility - twice as long as US law permits authorities to hold underage detainees. He later died.

While CPB said the cause of the teen's death was unknown in a statement Monday, during his stay at the facility Hernandez told staff he wasn't feeling well, and a nurse determined he had the flu, a border official told the press.

Hernandez is the fifth minor to die at a US immigrant holding center since last December.

The McAllen facility, a converted warehouse designed to hold 1,500 people, today houses some 2,400 detainees. The federal border agency, barely able to keep up with the influx of migrants, has already blown through this year's $12.5 million budget for McAllen and has requested another $12.5 million to keep the operation afloat.

Critics of loose immigration policies have long pointed to the risk of migrants carrying deadly diseases across borders, including President Donald Trump himself, who in 2015 claimed "tremendous infectious disease is pouring across the border."