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SAN ANTONIO, TX (CBSMiami) – A truck driver from Clearwater will face federal charges Monday after nine immigrants were found dead in a sweltering tractor trailer parked at a Walmart in San Antonio, Texas.

U.S. immigration investigators say more than 100 people may have been packed inside the 18-wheeler at one point, some had already been picked up, others fled.

The truck smuggling the immigrants into the U.S. was found with 39 people inside, including children. The conditions inside the truck were described as dire – no water and no working air conditioning – as temperatures soared to more than 100 degrees. Twenty of those inside were found in severe or critical condition.

“I just can’t imagine them being stuck in there dying when they thought they were coming here for a better life,” said Diandra Borrero.

The gruesome discovery was made after one person from the truck approached a Walmart employee and asked for water.

The truck is registered to Pyle Transportation of Iowa. The company has not commented but said they are conducting their own investigation.

Vigils and prayer services for the victims were held throughout San Antonia Sunday evening.

Investigators said the victims were from Mexico and Central America.

“When someone dies it’s not just some foreigner. It’s not just some animal. It’s another human being,” said Sen. Jose Menendez, D-TX.

Four of the survivors appeared to be between 10 and 17 years old. Investigators have not said where the rig came from or its final destination. Texas officials say it could take months to finish their investigation.