A person found dead near railroad tracks in San Antonio on Monday is believed to be connected to six other people whose remains were discovered in a cargo train boxcar near Laredo, Texas, officials said.

Laredo police responded after a Union Pacific employee reported a “trailer box car with the discovery of multiple casualties in the car” around 3 p.m. Sunday, police said.

The chief medical examiner for Webb County confirmed that five males and one female were recovered in Laredo.

The seventh person may have fallen off the train or been thrown out, which is why he was found in San Antonio, about 160 miles northeast of Laredo, said Javier Salazar, the sheriff of Bexar County, where San Antonio is located. The sheriff identified him only as a male.

“At this point, the prevailing theory is that he’s a resident of Mexico that was among the group that was being smuggled into the country in one of these shipping containers,” Salazar said at a news conference Monday.

The medical examiner’s office said in a news release that it believes the people in the Laredo group came from Mexico and Honduras. Mexico’s Foreign Affairs Ministry later confirmed that three of the dead are Mexican.

The ministry offered condolences and said the government will maintain contact with families of the dead and help arrange for the return of their bodies.

The medical examiner’s office identified two of the victims Monday as a 29-year-old woman from Mexico and a 24-year-old man from Honduras. An initial examination indicates the woman died of hyperthermia, the office said, noting temperatures reached as high as 105 degrees Sunday.

“While formal examinations for the remaining five individuals are still pending, it is highly probable that hyperthermia was the cause of death for the entire group,” it said.

The person found in San Antonio may also have died from heat-related illness. Salazar said a relative in another state called San Antonio police Saturday after getting a message from the victim saying he was in a boxcar and feeling ill because “it was getting very, very hot.”

Police were dispatched “several miles up the road” from where the person’s body was eventually found, Salazar said. After they learned of the bodies in Laredo, he said, officers returned and started patrolling up and down the train tracks until they found him.

One of the victims in the Laredo group, who has not yet been identified, appears to be a teenage boy, the medical examiner’s office in Webb County said.

It is unclear whether the victims were identified by fingerprint testing or another method.

The train’s origin was not immediately released. Jose Baeza, a Laredo police investigator, said that question was “at the crux of the ongoing fluid investigation.” He added that 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.

All of the victims’ cellphones have been turned over for “possible data to aid in identification,” and local authorities are in communication with consulates to identify the victims and contact their families, the medical examiner said.