Authorities in Matamoros are investigating what appears to be a tunnel used by drug smugglers.

Photos provided to Somos Noticias by Noticias Fronteradice show the tunnel, which is located near the Rio Grande south of Brownsville.

The Mexican Ministry of Defense is handling the investigation, said Tamaulipas Public Safety Director Alberto Rodriguez.

The U.S. Border Patrol and other law enforcement agencies are also investigating the tunnel.