SAN DIEGO -- Federal agents seized more than a ton of marijuana hidden in a van and trailer that entered the United States in San Ysidro this week, authorities reported Wednesday.

A service dog sniffed out the illicit cargo as a U.S. citizen tried to sneak it through a Customs and Border Protection inspection station on Monday morning, according to CBP public affairs.

The 2,500 pounds of cannabis was wrapped in 225 packages and secreted behind custom-built walls in the van and trailer, officials said.

The driver was arrested and booked into the Metropolitan Correctional Center in downtown San Diego. His name was not released.