Some 160 miles (250 km) from the US-Mexico border in San Antonio, 46 migrants were discovered to be dead on the back of a tractor-trailer last Monday in one of the country’s most deadly incidents of human smuggling in US history along the US-Mexico border amid rising border crossings and arrests.

According to authorities, a tractor-trailer was discovered sitting next to railroad tracks in San Antonio’s southwestern remote area, specifically at 9600 Quintana Road. San Antonio Police Chief William McManus reported that a person was working in a nearby building when they heard someone screaming for help around 5:50 pm. To their surprise, the individual opened the partially opened trailer doors and found stacks of bodies in the trailer after possibly dying from heat strokes, dehydration, and starvation, among other conditions.

According to San Antonio Fire Chief Charles Hood, 16 other people were found alive within the trailer – 12 adults and four minors, with reports that the individuals were “hot to the touch” as they were suffering from extreme exhaustion and heat strokes. He further noted that these people were too weak to get out of the trailer on their own, so they had to be assisted. The tractor-trailer was refrigerated, according to Hood, but there was no visible working air-conditioning unit on the truck. McManus stated that this was the most significant migrant-related incident in recent years.

“The patients that we saw were hot to the touch,” Hood said. “They were suffering from heat stroke, heat exhaustion. [There were] no signs of water in the vehicle. It was a refrigerated tractor-trailer, but there was no visible, working AC unit on that rig.”