SAN ANTONIO (AP) — A U.S. official says migrants were inside a tractor-trailer when it cleared an inland Border Patrol checkpoint.
The truck went through the checkpoint on Interstate 35 northeast of Laredo, Texas, according to the Justice Department.
The tractor-trailer ended up in San Antonio where 53 people were found dead.
It's the deadliest known smuggling attempt in the United States.
The Justice Department has arrested four men in connection with the smuggling operation. Two of the men are U.S. citizens and the other two are from Mexico, according to the DOJ.
The Mexican nationals were in the U.S. illegally, the DOJ stated.