Multiple dead bodies have been found in a boxcar train in Laredo, Texas ... TMZ has confirmed.

Laredo PD PIO tells TMZ … "We received call around 3:30pm today indicating possible deceased individuals in a cargo box."

LPD spokesman continues to say upon arriving to the scene, they requested assistance from the fire department, whom confirmed 6 individuals were deceased. We're told it is still an active scene and authorities are still working on the investigation.

Authorities tell us no ages or genders have been determined, it is still unknown how long the deceased individuals have been there as they are still pending reports -- cause of death will be determined by the Medical Examiner’s office. The deceased individuals' immigration status are also unknown at this time.

In regard to online speculation, LPD PIO tells us weather could be a factor due to Laredo’s intense heat, but that will be a part of the investigation and ME report, so it's all just speculation at this time.

A Union Pacific spokesperson tells TMZ … "Union Pacific is saddened by this incident and is working closely with law enforcement to investigate."