Seventh Body Found Near San Antonio Linked to Six Heat Deaths in Laredo Boxcar

A man found dead Monday by railroad tracks southwest of San Antonio, Texas, is believed connected to six people who likely died of heat stroke inside a shipping container near the Mexico border, authorities said.

Bexar County Sheriff Javier Salazar said the seventh body turned up nearly 150 miles north of a Union Pacific rail yard in Laredo, where the six bodies were discovered Sunday afternoon. U.S. Immigration and Customs Enforcement told CBS News it is investigating the boxcar deaths as a potential human smuggling case.

Investigators located the seventh person after an alert showed one of the containers had been opened over the weekend near the site, Salazar said. "On these trains, there is a sensor on some of the containers that alerts whenever a container's opened," he told reporters. "Once those bodies were found in Laredo, they came back to this location here and started patrolling up and down the railroad tracks until such time that they found him."

Salazar noted the container cannot be opened from the inside. The train carrying the body found Monday came from Del Rio and split near San Antonio, with one half headed to Laredo and the other to Houston. That raises the possibility more people were once inside the container.

"At this point, we don't know if it was opened to let people that made it out successfully or they just opened it to dump the body," Salazar said. The man carried Mexican identification, the sheriff added.

San Antonio police got a report Saturday from a relative of one of the people inside the container. The relative, who lives in another state, called to say they received a message that "it was getting very, very hot and they were having some physical trouble as a result of it," Salazar said. Officials believe the person who sent the message is among the six dead.

Webb County Medical Examiner Dr. Corinne Stern, who is performing the autopsies, said the individuals came from Mexico and Honduras. An autopsy on a 29-year-old Mexican woman showed she died of hyperthermia, or heat stroke. "I've ruled that an accidental death," Stern said. "I believe that the remaining individuals probably all succumbed to heat stroke as well, but their exams are not completed at this time, so I will not rule on their cause and manner yet."

Temperatures hit 97 degrees in Laredo Sunday afternoon, which likely made it feel hotter than 100 degrees inside the boxcar, according to CBS affiliate KENS-TV.

Union Pacific said Sunday it was "saddened by this incident and is working closely with law enforcement to investigate."