Six bodies were mysteriously discovered inside a train boxcar in Laredo, Texas, on Sunday, according to authorities.

A Union Pacific worker stumbled upon the dead bodies in a train yard at a remote location near the Mexican Border, according to Laredo ​Police Investigator Joe Baeza.

Cops and firefighters at the scene confirmed the six people had died, but authorities have not yet determined the cause of their deaths, police said.

“Union Pacific is saddened by this incident and is working closely with law enforcement to investigate,”  Daryl Bjoraas, a spokesman for Union Pacific, said in a statement to The Post.

There were no survivors, and police have not said where the individuals were from.

“Imagine a loading dock at a seaport, but for trains,” Baeza explained to NBC News. “This is where they load and unload a lot of rail cars.”

Previous instances of deaths in train cars near the US-Mexico border have been related to migrants and human smuggling operations — including the 53 migrants who were found in the back of a sweltering tractor-trailer in Texas in 2022.

In 2023, 12 migrants, including two who were dead, were found inside a locked train car that had been sitting in sweltering temperatures 20 miles east of Uvalde.

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

An investigation into the incident remains ongoing.

With Post wires