SAN ANTONIO — The bodies of at least 46 people believed to be migrants who crossed into the United States from Mexico were found dead on Monday in and around a tractor-trailer that had been abandoned on the outskirts of San Antonio, Gov. Greg Abbott of Texas said.
More than a dozen others were found alive and taken to local hospitals, according to two officials briefed on the police response, who spoke on the condition of anonymity to discuss details of what appeared to be one of the worst episodes of migrant death in the United States in recent years.
Officers from the San Antonio Police Department were searching for the driver of the vehicle, who appeared to have abandoned it sometime before it was discovered in a remote area near railroad tracks and auto salvage yards southwest of downtown, the people said.
State officials in Texas, already managing record levels of migrant crossings from Mexico, have been bracing for a new surge this spring and summer. All of the victims were believed to have crossed into the United States illegally and been brought north. The closest border crossing is roughly 140 miles away.
It was not immediately clear how the people had died, but San Antonio and other cities across Texas have been experiencing heat in June that is at or near record levels. The temperature on Monday in the city had topped 100 degrees.
A spokesman for the Texas State Police referred questions to the San Antonio Police Department, which did not respond to requests for comment. The Department of Homeland Security was expected to take over the investigation.
Ruby Chavez, 53, a housewife who lives about a mile away from where the truck was found, heard about the discovery on television, then saw a helicopter churning overhead. She came to the scene with her husband, Ruben, to pray.
The area was a location known to locals as a “drop-off spot” for migrants, the couple said.
“You can tell they just get here. We see them with backpacks or asking for food or money,” Ms. Chavez said. “It’s sad. And now I’m hearing there are kids.”
Her husband added: “They know this area. They jump off the train and get picked up.”
Dozens of police officers and fire officials massed around the scene along Quintana Road, where the truck was found, a road sandwiched between train tracks and auto salvage yards that has a rural feel despite being inside the city limits. Several farms are nearby.
Smugglers often transport large numbers of migrants in trailers, vans or S.U.V.s after meeting them in remote areas once they have managed to enter the United States. San Antonio is a major transit point for migrants making their way from Texas to points across the United States, and tens of thousands of migrants have passed through the city in recent months, according to immigrant advocates.