(CNN) -- U.S. border patrol agents Friday found a crude tunnel, apparently used for smuggling, underneath the concrete-lined Rio Grande River near El Paso, Texas.

The discovery came as authorities were investigating suspicious activity in the city storm drain system and came upon a juvenile from Mexico with 200 pounds of marijuana.

"This is another example of smuggling organizations actively recruiting juveniles to smuggle narcotics and humans," said sector Chief Randy Hill. "These organizations are exploiting the youth of Mexico and putting their lives in danger."

Mexican authorities were called in to locate the tunnel entrance on the Mexican side.