Los Angeles (AFP) - A major Texas border station has been temporarily closed due to a fever outbreak, officials said, one day after a Guatemalan teenager diagnosed with flu at the facility died in immigration custody.

Medical staff imposed the quarantine at the McAllen processing center after a "large number" of detainees were found to have high fevers and symptoms of a flu-related illness.

"To avoid the spread of illness, the Rio Grande Valley Sector has temporarily suspended intake operations at the CPC," Customs and Border Protection said in a statement late Tuesday, referring to the Central Processing Center.

"Medical staff are currently working to provide all subjects with proper medical treatment."

People detained in Rio Grande Valley will be held in other stations until the situation is resolved, it said.

A 16-year-old boy died Monday in immigration custody in Texas, becoming the fifth child from Guatemala to die since December after being apprehended by US border patrol agents.

The boy, identified as Carlos Gregorio Hernandez Vasquez, had been detained on May 13 after crossing the border, and was processed at the McAllen center, according to US media reports.

He was seen by a nurse who determined he had the flu and moved to a nearby facility at Weslaco to avoid other detainees getting sick.

He was found unresponsive Monday during a welfare check, an hour after agents had last checked on him.

The Border Patrol agency has come under intense scrutiny in recent months over its treatment of children apprehended at the border.

Border enforcement officials earlier this year said the country's immigration system had reached a "breaking point" of illegal border crossings that have overwhelmed the system, especially in the Rio Grande Valley.

Almost half a million people have been stopped at the southern US border since October. Most who cross without authorization surrender to authorities and file for asylum.

Overcrowding at emergency shelters has forced authorities to release some migrants from detention as they await a review of their asylum applications.

The McAllen center is one of the busiest along the US-Mexican border.