At least two people were found dead in a train car, Uvalde Mayor Don McLaughlin told Texas Public Radio.
At least five others were hospitalized, McLaughlin said.
Authorities closed off a section of Highway 90 between the towns of Knippa and Sabinal so medical helicopters could land safely.
The train had been sitting on the tracks for around three hours under the afternoon sun, McLaughlin told TPR.
"911 got a call -- don't know if it was from a family member or one of the migrants who were locked in the shipping container," McLaughlin said.
Uvalde Police Department and the Southwest Texas Regional Advisory Council provided the Uvalde mayor with the information, the report said.
McLaughlin described the medical response as “enormous,” according to the report.
"There were more people than we had ambulances available in Uvalde [for the Robb Elementary school shooting in May 2022],” he said.
“We called them in from everywhere -- Kerrville, San Antonio, Hondo, and locally in Uvalde."
A Department of Homeland Security probe will determine whether the case involves human smuggling, the report said.
