The bodies of 46 dead immigrants have been found inside a truck trailer in San Antonio, Texas, on the US-Mexico border while entering the United States illegally.

Their bodies were found inside the trailer of a truck parked next to a railway track in a remote area on the southern outskirts of the city, a San Antonio Fire Department official said. According to the preliminary investigation of the police, it is estimated that they died due to high temperature and lack of water inside the trailer of the truck.

Police said that three suspects have been detained during the preliminary investigation of the incident. The U.S. Department of Homeland Security said in a statement that it is investigating the “alleged human trafficking” in coordination with local police.

Republicans have criticized Biden’s border strategy ahead of the midterm congressional elections in November, who vowed to reverse Donald Trump’s tough immigration policies.