Six bodies were found on Sunday in a train boxcar in Laredo, Texas, according to police.
A Union Pacific worker discovered them in a train yard at a remote location near the Mexican border, and police and firefighters later confirmed they had died, said Laredo Police Investigator Joe Baeza.
Police have not determined how they died, Baeza said. The investigation is ongoing, he said.
There were no survivors, he said.
Police did not say where the individuals were from.
Past instances of multiple deaths in trains and tractor trailers not far from the U.S.-Mexico border have involved migrants, including a 2022 incident in which 53 were found dead in an abandoned truck with malfunctioning air conditioning on the outskirts of San Antonio.