SAN ANTONIO, Texas, July 23 (Reuters) - At least nine men were found dead on Sunday alongside dozens of people discovered inside a sweltering tractor trailer parked at a Walmart store in San Antonio, Texas, in what authorities called a case of "ruthless" human trafficking.
Thirty people, many in critical condition and suffering from heat stoke and exhaustion, were removed from the trailer, which lacked air conditioning or a water supply, San Antonio Fire Chief Charles Hood said. Temperatures outside the vehicle topped 100 degrees Fahrenheit (37.8 Celsius).
Another person was found in a wooded area nearby and was also being treated, the U.S. Attorney's Office for the Western District of Texas said in a statement. All the deceased were adult males, it said.
Authorities initially said eight bodies were found in the trailer, but the U.S. Attorney's Office statement later said the death toll had risen to nine.
"All were victims of ruthless human smugglers indifferent to the well-being of their fragile cargo," San Antonio-based U.S. Attorney Richard Durbin Jr. said.
"These people were helpless in the hands of their transporters. Imagine their suffering, trapped in a stifling trailer in 100-plus degree heat," he said.
The truck's driver, identified by the U.S. Attorney's Office as James Mathew Bradley Jr., 60, of Clearwater, Florida, was arrested in connection with incident, the statement said.
A criminal complaint will be filed in federal court in San Antonio on Monday morning, and Bradley is expected to have an initial court appearance shortly afterwards, the U.S. Attorney said. Meanwhile, a multiagency investigation was underway.
The bodies of the deceased, who have not yet been identified by authorities, were discovered after officials were led to the trailer by a man who had approached a Walmart employee and asked for water.
San Antonio is about 150 miles (240 km) north of the border with Mexico. Temperatures in the area held above 100 degrees Fahrenheit until 6 p.m. local time on Saturday and were expected to soar into the 100s again on Sunday, with humidity making the heat feel close to 110 degrees, forecasters said.
Raids on suspected illegal immigrants have ramped up across the United States in recent months, after President Donald Trump's vow to crack down on those entering the country without authorization or overstaying their visas.
In Texas alone, federal immigration agents said they arrested 123 illegal immigrants with criminal records in an eight-day operation that ended last week.
The San Antonio deaths come more than a decade after what is considered the worst immigrant smuggling case in U.S. history, when 70 people were found stuffed into an 18-wheeler. Nineteen of them died in the incident in Victoria, Texas, about 100 miles southeast of San Antonio, in May 2003.
San Antonio Police Chief William McManus described the latest fatalities as a "horrible tragedy" and said other suspects had fled the scene as police officers arrived.
"Checking the video, there were a number of vehicles that came and picked up other people who were in that trailer," McManus said.
Twenty people were airlifted to seven hospitals in conditions ranging from "critical to very critical," Hood said. Eight others are hospitalized in less serious condition, he said.
McManus said the people in the truck ranged from school-age juveniles to adults in their 20s and 30s.
He said the Department of Homeland Security had joined the investigation, and that the origin of the truck is unclear.
Experts have warned in recent months that tougher immigration policies could make it more difficult to stop human trafficking. Measures to harden international borders encourage would-be migrants to turn to smugglers and fear of deportation deters whistle-blowing, they said.
U.S. Immigration and Customs Enforcement (ICE) officials defended the use of tough methods to fight human smuggling.
"So long as I lead ICE, there will be an unwavering commitment to use law enforcement assets to put an end to these practices," the agency's acting director, Thomas Homan, said in a statement.
The Border Patrol has regularly reported finding suspected immigrants inside trucks along the U.S. border with Mexico. Earlier this month, 72 Latin Americans were found in a trailer in Laredo, it said. In June, 44 people were found in the back of tractor trailer in the same Texas city, which lies directly across the Rio Grande from Mexico.
San Antonio has a policy of not inquiring about the immigration status of people who come into contact with city officials or police.
It was among several "sanctuary cities" in Texas that filed a federal lawsuit last month to block a new state law set to take effect in September that would force them to cooperate closely with immigration agents.
"San Antonio will not turn its back on any man, woman, or child in need," Mayor Ron Nirenberg said in a statement responding to the truck deaths. (Additional reporting by Barbara Goldberg in New York; Editing by Frank McGurty and Daniel Wallis)