San Antonio Police Department confirmed the death of at least 46 people inside a tractor-trailer on Monday. It is being considered a migrant smuggling attempt into the United States and further investigations are being launched by law enforcement officials.

Hours after the incident, San Antonio Police Chief William McManus shared initial assessments made by the officers. He confirmed that 16 people were taken to the hospital after the incident, out of which 12 were adults and four were children.

Also Read: Texas tractor-trailer deaths: Governor Greg Abbott pins blame on Joe Biden

McManus said that at least three people have been taken into custody by police officials so far. However, it was unclear if they were absolutely connected with human trafficking. The United States Homeland Security Investigations will be taking charge of the probe.

In agreement with initial reports, McManus hinted that the deaths could have been caused by severe temperatures. No official cause of death has been revealed so far. The patients were hot to the touch and dehydrated, and no water was found in the trailer, McManus said on Monday.

While describing police officials’ first response, the SAPD chief said that a city worker at the scene was alerted to the situation by a cry for help shortly before 6 PM. Officers arrived to find a body on the ground outside the trailer and a partially opened gate to the trailer, he added, according to reports from Associated Press.

Also Read: US officials arrests over 200,000 migrants crossing Mexico border in March

Such incidents of alleged border crossings have been reported before, however, the recent death is likely to be the highest in decades.

Ten migrants died in 2017 after being trapped inside a truck that was parked at a Walmart in San Antonio. In 2003, 19 migrants were found in a sweltering truck southeast of San Antonio.