At least 39 people, most of them undocumented US-bound migrants who had just survived a perilous jungle crossing, died in a bus crash in Panama early Wednesday, officials said.

Panama's National Migration Service said the injured, including children, were being treated at various hospitals and clinics, without saying how many there were.

The latest death toll, it added, was based on "preliminary information."

The bus had "66 passengers on board" when it plunged down a ravine and hit a minibus some 400 kilometers (250 miles) west of the capital Panama City, the press statement said, according to AFP reports.

The bus was transporting migrants who had crossed the Darien Gap -- an inhospitable  jungle area bordering Colombia -- and were moving westward toward Costa Rica from where they aimed to continue their journey through Central America and Mexico, and ultimately to the United States.

The bus was on its way to a hostel in Gualaca near the Costa Rica border, where the passengers were to have rested before continuing their journey.

Local media said the crash happened as the driver was turning the bus around after missing the hostel.

It allegedly left the road on a bend and plunged down a ravine, hitting a rock and a minibus on a road below.

"We saw it coming and dived under the seats, the driver and myself, and because of that nothing happened to us," Edgar Guerra, one of the two people inside the minibus, told local media.

The nationalities of the occupants has not been revealed but Cuba's foreign minister Bruno Rodriguez said on Twitter that Cubans were among the dead.

- 'Great sadness' -

President Laurentino Cortizo tweeted his "great sadness" at learning of the accident at Gualaca.

"This is regrettable news for Panama and the region," he said, extending his government's condolences to the next of kin.

"Government teams work hard on the ground, providing medical assistance to survivors of this tragedy," the president added.

Several people were taken by ambulance to a hospital in the Chiriqui provincial capital city David, according to authorities.

Among them were 10 children aged between four and 11, including three in "critical condition," the hospital's director Johny Parra said.

Thousands of migrants arriving via Colombia risk their lives every year beating a path through the thick, swampy Darien Gap, a roadless jungle area replete with wild animals, dangerous rivers and criminal gangs.

According to Jose Vicente Pachar, director general of the Institute of Legal Medicine and Forensic Sciences of Panama, at least 60 migrants died crossing the Darien Gap in 2022, up from 50 in 2021.

The impenetrable topography has meant that plans to build a missing stretch of the Pan-American Highway through the Darien Gap have never been realized.

- 'Risk' -

Despite the dangers, the number of irregular migrants arriving in Panama en route to the United States nearly doubled in 2022 to a record 248,000, the immigration authority reported on January 1.

More than half were Venezuelan, the rest included Ecuadorans, Haitians and Cubans, as well as people from Africa and Asia.

The government of Panama, in collaboration with United Nations agencies and aid organizations, has set up camps to provide humanitarian assistance to the never-ending migrant arrivals.

In his tweet, Cortizo reiterated his government's "commitment to continue providing humanitarian aid and dignified conditions to face irregular migration."

Panamanian authorities help transfer migrants, hundreds every day, in private buses from the border with Colombia to Paso Canoas on the border with Costa Rica.

It is a journey of some 700 kilometers and about 10 hours for which the migrants buy a ticket.

"It is lamentable this traffic accident, these are people looking for better living conditions," Panama's national director of migration Samira Gozaine told the Telemetro broadcaster as she underlined "the risk" people take on this journey.

She said migrant buses to Paso Canoas usually travel at night when there is less traffic and conditions are cooler.