At least 46 people were found dead inside a tractor-trailer in San Antonio, Texas.

According to authorities, 16 more people were transferred to local hospitals.

San Antonio Police Chief Bill McManus reported that a passerby heard cries for help and discovered the tractor-trailer with the casualties inside.

ABC News reported that the trailer was refrigerated but seemed to have been lacking working air-conditioning.

San Antonio Fire Department Chief Charles Hood reported that the 16 people that were transported to hospitals were suffering from heat stroke and heat exhaustion. No children died in the incident.

According to ABC News, officials said that three people were arrested following the incident which is now under a federal investigation.

Immigration and Customs Enforcement (ICE) confirmed that the incident is being treated as a suspected case of human smuggling.

"The criminal investigation remains ongoing," an ICE spokesperson said.