The six were discovered near a Union Pacific rail yard Sunday afternoon. What caused their deaths wasn’t immediately clear.

Shimmering heat distorts a view of a yellow Union Pacific freight engine approaching with its headlights on in bright sunlight.

A Union Pacific freight train in Hutto, Texas last year. A spokesperson said the company was “saddened” after six people were found dead in a cargo train boxcar in Laredo.

Six people were found dead in a cargo train boxcar near a Laredo, Texas, rail yard Sunday, officials said.

Police responded after a Union Pacific employee called to report a “trailer box car with the discovery of multiple casualties in the car” around 3 p.m. local time, police said.

The ages of the victims and the origin of the train were not immediately released. Jose Baeza, an investigator with the Laredo Police Department, said those questions are “at the crux of the ongoing fluid investigation.”

The Webb County medical examiner will conduct an autopsy to determine the cause and manner of death, police said.

Baeza said the rail yard is miles long.

“Imagine a loading dock at a seaport, but for trains,” he said in a phone interview. “This is where they load and unload a lot of rail cars.”

A Union Pacific spokesperson said in a statement that the company is “saddened by this incident” and is “working closely with law enforcement to investigate.”

Laredo, which borders Mexico, has one of Texas’s largest ports of entry facilitating commercial trade. As of 2024, Port Laredo accounted for 62% of the state’s land port trade, valued at nearly $340 billion, according to data collected by the Texas Comptroller of Public Accounts.

Temperatures in Laredo on Sunday hit a high of 97 degrees, according to the National Weather Service.