Two people were dead and 10 others hospitalized after an unknown medical emergency Friday on board a freight train in Uvalde County, Texas, authorities said.
The patients were assumed to be migrants, according to Uvalde city police. As many as 15 people needing medical attention were found on the train after it was stopped a few miles west of Knippa, police said.
Two were pronounced dead at the scene, police said. Of 10 others hospitalized, four were flown to facilities in San Antonio, Union Pacific said in a statement.
Most of the patients — 12, including the two who died — were found in a shipping container, the railway said. Three other people were found in a “hopper car,” used to transport bulk material such as grain or coal, it said.
Uvalde police said an unknown caller dialed 911 about 3:50 p.m. to report the medical emergency, saying numerous people were "suffocating" inside a train car.
Additional details about what happened weren't immediately released.
University Health, a system that runs San Antonio's top-level trauma center, University Hospital, said in a statement it was caring for a man in critical condition and another in serious condition.
The weather in Uvalde was warm enough — temperatures topped out at 87 degrees Friday — that the National Weather Service issued a hazardous weather outlook bulletin warning of "near-critical fire weather" in parts of the county.
Police said the discovery was under investigation by Union Pacific special agents. U.S. Customs and Border Protection said requests for information should go to the Uvalde County Sheriff’s Office, which did not immediately respond to an inquiry.
In its statement, Union Pacific said it was "deeply saddened by this incident and the tragedies occurring at the border. We take the safety of all individuals seriously."
Knippa is a town of 808 people east of Uvalde, along the U.S. Highway 90 corridor that leads to San Antonio.
In June, 50 adults and three children died after a tractor-trailer they were in was found in San Antonio amid stifling heat.
Two men were indicted on federal allegations of migrant smuggling resulting in death and other counts.
This article was originally published on NBCNews.com