San Antonio police officers investigate the scene where people were found dead on Sunday in a tractor-trailer outside a Wal-Mart store in stifling summer heat.

SAN ANTONIO -- At least nine people died after being crammed into a sweltering tractor-trailer found parked outside a Wal-Mart in the midsummer Texas heat, victims of what authorities said on Sunday was a people-smuggling attempt.

The driver was arrested, and nearly 20 others rescued from the rig were hospitalized in dire condition, many with extreme dehydration and heatstroke, officials said.

"We're looking at a human-trafficking crime," said San Antonio Police Chief William McManus, calling it "a horrific tragedy."

Authorities were called to the San Antonio parking lot late Saturday or early Sunday and found eight people dead inside the truck. A ninth victim died at the hospital, said Liz Johnson, a spokesman for U.S. Immigration and Customs Enforcement.

[U.S. immigration: Data visualization of selectedimmigration statistics, U.S. border map]

The victims "were very hot to the touch. So these people were in this trailer without any signs of any type of water," San Antonio Fire Chief Charles Hood said.

Authorities would not say whether the trailer was locked when they arrived, but they said it had no working air conditioning.

The eight initial fatalities were believed to have been caused by heat exposure and asphyxiation, a spokesman for the Police Department said. Federal officials said in a statement that 39 people were in the trailer. Hood said at a news conference that 30 were taken to hospitals, about 20 of whom were in "extremely severe" or critical condition.

Two of those found were "school-age children," and the others were in their 20s and 30s, McManus said. The two youngest of those injured were 15, according to a spokesman. The bodies were taken to the Bexar County medical examiner's office to determine the cause of death. Details about the victims were unavailable.

Mayor Ron Nirenberg in a statement called the episode "tragic," adding that it "shines a bright light on the plight of immigrants looking for a better life and victims of human trafficking."

"These people were helpless in the hands of their transporters," said Richard Durbin Jr., the U.S. attorney for the Western District of Texas, which includes San Antonio. "Imagine their suffering, trapped in a stifling trailer in 100-plus-degree heat."

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Shoppers returned to the Wal-Mart store on Sunday.

"Who couldn't be angry?" Mario Martinez, 50, an air-conditioning service worker from San Antonio, said as he pumped refrigerant into his car.

He said residents of the central Texas area were familiar with such cases because San Antonio is on the Interstate 35 corridor that smugglers use to transport drugs and people.

It is the latest smuggling-by-truck operation to end in tragedy. In one of the worst cases on record in the U.S., 19 people locked inside a stifling rig died in Victoria, Texas, in 2003.

Based on initial interviews with survivors, more than 100 people may have been packed into the back of the 18-wheeler at one point in its journey, Immigration and Customs Enforcement acting Director Thomas Homan said. Officials said 39 people were inside when rescuers arrived, and the rest were believed to have escaped or hitched rides to their next destination.

Some of the survivors told authorities they were from Mexico, and four appeared to be between 10 and 17 years old, Homan said. Investigators gave no details on where the rig began its journey or where it was headed.

Homan said it was unlikely the truck was used to carry the people across the border into the United States. He said people from Latin America who rely on smuggling networks typically cross the border on foot and are then picked up by a driver.

"Even though they have the driver in custody, I can guarantee you there's going to be many more people we're looking for to prosecute," Homan said.

Federal prosecutors said James Mathew Bradley Jr., 60, of Clearwater, Fla., was taken into custody and would be charged today. The area U.S. Attorney's Office wouldn't say whether Bradley was the driver who was arrested. It was not immediately known whether Bradley had an attorney who could speak on his behalf.

The U.S. Homeland Security Department stepped in to take the lead in the investigation from San Antonio police.

Department Secretary John Kelly said the incident demonstrates the brutality of smuggling organizations that "have no regard for human life and seek only profits."

The truck had an Iowa license plate and was registered to Pyle Transportation Inc. of Schaller, Iowa. A company official did not immediately respond to a phone message seeking comment.

San Antonio is about a 150-mile drive from the Mexican border. The temperature in San Antonio reached 101 degrees on Saturday and didn't dip below 90 degrees until after 10 p.m.

An expert on border enforcement and migrant deaths called the trucks "mobile ovens."

"Those things are made out of steel and metal," the expert, Nestor Rodriguez, a sociology professor at the University of Texas at Austin, said Sunday. "Yesterday in Austin, it was like 96 degrees at 9:30 in the evening. Even if the cooling system is on in the tractor-trailer, it's just too hot."

The tragedy came to light after a person from the truck approached a Wal-Mart employee in the parking lot and asked for water late Saturday night or early Sunday morning, said McManus, the local police chief.

The employee gave the person water and then called police. Some of those in the truck ran into the woods, McManus said.

Investigators checked store surveillance video, which showed vehicles arriving and picking up people from the truck, authorities said. Wal-Mart released a brief statement Sunday saying it was doing what it could to help investigators.

In the May 2003 case, the aliens were being taken from South Texas to Houston.

Prosecutors said the driver heard them begging and screaming for their lives but refused to free them. The driver was sentenced to nearly 34 years in prison.

"It's sad that 14 years later people are still being smuggled in tractor-trailers, there still isn't water, there still isn't ventilation," Homan said.

"These criminal organizations, they're all about making money. They have no regard for human life."

The Border Patrol has reported at least four truck seizures this month in and around Laredo, Texas. On July 7, agents found 72 people crammed into a truck with no means of escape, the agency said. They were from Ecuador, El Salvador, Guatemala and Mexico.

Authorities in Mexico have also made a number of such discoveries over the years.

Last December, they found 110 migrants trapped and suffocating inside a truck after it crashed while speeding in the state of Veracruz. Most were from Central America, and 48 were minors. Some were injured in the crash.

Last October, also in Veracruz state, four migrants suffocated in a truck carrying 55 people.

About 100 people held a vigil in San Antonio on Sunday night.

Rights activists and church officials held up handmade signs reading "Who here is not an immigrant" on Sunday evening in the plaza outside the San Fernando cathedral in downtown San Antonio. One woman wore a T-shirt reading in Spanish, "My name is Jesus. I don't have papers."

Those gathered held a moment of silence, then gave speeches blaming federal and Texas authorities' embrace of harsher immigration policies for contributing to the deaths.

Jonathan Ryan, executive director of the nonprofit Refugee and Immigrant Center for Education and Legal Services, said it's "an unfortunate example" of what happens when such polices are enacted.

He said: "You can change laws but you cannot stop the movement of displaced people."

A new law approved by the Texas Legislature lets police inquire about peoples' immigration status during routine interactions like traffic stops. Opponents have sued in federal court to stop it, saying it's a "show your papers" law.

Information for this article was contributed by Eric Gay, Will Weissert, Mike Graczyk, Elliot Spagat and Peter Orsi of The Associated Press; and by David Montgomery, Manny Fernandez, Yonette Joseph, Ron Nixon and Nicholas Kulish of The New York Times.

A Section on 07/24/2017