U.S. Customs and Border Patrol (CBP) agents in Tucson, Arizona arrested and charged filed human smuggling charges against two U.S. citizens.

On Monday night, CBP agents assigned at the Interstate 19 Immigration Checkpoint found 33 Mexican and Ecuadorian nationals hidden inside a semi-tractor-trailer.

Agents discovered the immigrants after a Border Patrol canine alerted them to the semi-tractor-trailer, which underwent a secondary inspection. They x-rayed the vehicle and images showed dozen of people inside.

According to the agency, the U.S. citizens, a driver and his passenger, locked the immigrants in the semitrailer’s produce cargo, which had temperature of 47 degrees Fahrenheit. They endangered the lives of the immigrants, who were only wearing short-sleeved T-shirts and long pants.

The agents arrested and processed the immigrants for violating U.S immigration laws. They did not release the names of the U.S. citizens charged with human smuggling violations.

The Department of Homeland Security (DHS) launched “Operation Safeguard” to prevent deaths of immigrants at the hands of smugglers. It also aims to educate the public and the trucking industry regarding the life-threatening dangers of smuggling humans using commercial conveyances.

Yuma Border Patrol agents in partnership with Mexican officials arrest murder suspect

Separately, the CBP announced on Thursday that agents at the Yuma Sector Foreign Operations Branch in partnership with Mexican officials arrested a wanted murder suspect hiding in Mexico.

According to the agency, Yuma Border Patrol agents received information from the Sonoran State Police regarding their encounter with a person who claimed to be a U.S. citizen. The agents checked record and verified that the person is a U.S. citizen and is wanted for murder by the Pinal County Sheriff’s office.

The Mexican officials transferred custody of the murder suspect to the Pinal County Sheriff’s office.

In a statement, Yuma Sector Deputy Chief Patrol Agent Carl E. Landrum, said, they “consistently conduct binational collaboration efforts with our Government of Mexico partners to enhance public safety in both the United States and Mexico.”

He added, “We integrate efforts and incorporate partnerships with local, state, federal, tribal, and international law enforcement entities who are likewise charged with protecting our citizens and communities to fulfill our mission of border and national security.”