Rail workers in Texas found six people dead inside a boxcar at a yard close to the Mexican border on Sunday afternoon, officials said.

The discovery was made by a Union Pacific employee inspecting the stopped train at the yard in Laredo before it continued its journey north, a spokesperson for the Laredo police department said, citing the railroad freight company.

Authorities are working to establish a cause of death for the six, who were found at about 2.30pm local time on an afternoon when temperatures climbed above 90F (32C). Nobody was found alive in the boxcar, the spokesperson said.

“It’s a very unfortunate event.…