A US official says the death toll from people found in the back of a sweltering tractor-trailer in a San Antonio Walmart car park has risen to 10.
Authorities say they were the victims of "ruthless" human traffickers.
Thomas Homan, acting director of US Immigration and Customs Enforcement, told The Associated Press on Sunday that two people died in a hospital. Eight dead bodies were found in the truck.
Based on initial interviews with survivors, Mr Homan said there may have been more than 100 people in the truck. Thirty-eight were found inside. The rest are believed to have fled or been picked up.
Severa are in critical condition and suffering from heat stroke and exhaustion. The trailer lacked air conditioning or a water supply, San Antonio Fire Chief Charles Hood said on Sunday.
The victims are believed to be Mexican nationals.
The truck's driver was arrested and will be charged, said Richard Durbin, US Attorney for the Western District of Texas, and prosecutors will work to identify others responsible.
The bodies were discovered after officials were led to the trailer by a man who had approached a Walmart employee and asked for water.
"All were victims of ruthless human smugglers indifferent to the wellbeing of their fragile cargo," Mr Durbin said.
The temperature had been close to 40degC throughout Saturday evening, and was expected to be hot again on Sunday.
San Antonio Police Chief William McManus described the deaths as a "horrible tragedy" and said other suspects had fled the scene as police officers arrived. Twenty people were airlifted to seven hospitals and their conditions were "critical to very critical", Mr Hood said. Eight others are hospitalised in less serious condition, he said.
At San Antonio's University Hospital, six adults were admitted early Sunday with heat-related injuries, all of them in critical condition, spokesman Donald Finley said.
McManus said the people in the truck ranged from school-age juveniles to adults in their 20s and 30s.
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.
While there are no official law enforcement statistics, nearly 32,000 cases of human trafficking in the United States have been reported to the National Human Trafficking Hotline in the last decade.
Reuters / Newshub.