The boy, who died at a shelter facility in Florida, was identified by the Honduran foreign affairs office as Ángel Eduardo Maradiaga Espinoza.

The US Department of Health and Human Services (HHS) acknowledged the death in a statement that did not name him or say how he died.

US officials have braced in recent days for an influx of border crossings.

On Friday, Enrique Reina, the secretary of foreign affairs in Honduras, said on Twitter the death had occurred at a shelter in Safety Harbor, a city on the Tampa Bay coastline in western Florida.

The shelter is managed by the HHS Office of Refugee Resettlement (ORR), which is in charge of housing and caring for unaccompanied migrant children.

Mr Reina said his government was in contact with the teenager's family and called for "an exhaustive investigation" into the circumstances of his death.

The boy had been in US custody for five days, a source told CBS News, the BBC's US partner. He was found unconscious on Wednesday morning, taken to a local hospital and was pronounced dead an hour later, the source added.

A federal official told CBS there had been "no altercation of any kind" involved in the death.

The teenager "wanted to live the American Dream" his mother, Norma Saraí Espinoza Maradiaga, told the Associated Press.

"He told me he was in a shelter and not to worry because he was in the best hands," she said in a phone interview. "We only spoke two minutes, I told him goodbye and wished him the best."

A medical examiner's investigation is currently underway. Bill Pellan, director of investigations, told US media that a cause of death has yet to be determined. He said hospital staff had failed to resuscitate the boy.

Border officials are required by law to place unaccompanied minors in ORR care within 72 hours of apprehension. The ORR then houses these children in shelters and other facilities nationwide until they turn 18 or are claimed by a US-based sponsor.

Deaths in ORR custody are rare, according to Aura Bogado, a senior reporter at the Center for Investigative Reporting, but CBS reports that a four-year-old child from Honduras described as "medically fragile" died from a cardiac arrest event in March while in HHS custody in Michigan.

In 2019, the outlet also reported that six migrant children - some with health issues - were known to have died over the past year, either after being detained by border patrol or after being released by HHS to a hospital.

In its statement on Friday, the HHS said it was in touch with the child's family and was "reviewing all clinical details of this case, including all inpatient health care records" per standard practice.

The department cited "privacy and safety reasons" for its inability to share further information on the child's death.

News of the death follows the overnight expiry of Title 42, a pandemic-era border policy used to swiftly expel migrants who cross illegally.

Officials had expressed concern about a possible influx of migrants in the coming weeks, possibly leading to overcrowded detention and shelter facilities.

But HHS officials said there has been no substantial increase in migrants processed into custody on Friday, and it is not clear if the minor's death is related to the lifting of Title 42.

The White House is "certainly aware of the tragic loss, and our hearts go out to the family", press secretary Karine Jean-Pierre said on Friday.

She declined to comment further until the medical investigation concludes, adding she did not know if President Biden had yet been briefed on the death.

Government figures show that more than 8,000 unaccompanied migrant minors are currently under HHS care, with an average custody period of 29 days.

Over the last fiscal year, three in 10 migrant minors in US custody came from Honduras.