(CNN) -- US Border Patrol agents arrested a man allegedly attempting to smuggle approximately 250 pounds of fentanyl in his truck's spare tire and gas tank near the Mexican-California border Monday, the agency said.

Agents who searched the man's vehicle found several bundles of pills that tested positive for fentanyl, US Customs and Border Protection announced in a news release. The agency estimates the stash has a street value of $3,679,000.

The driver, an adult male and US citizen, was arrested and turned over to the DEA along with the drugs, the agency said. The truck was seized by Border Patrol.

The smuggling attempt was discovered after a K-9 unit flagged a black GMC truck during a vehicle stop near Campo, California, about ten miles from the Mexican border, the agency said.

"Our agents prevented these dangerous narcotics from reaching our communities," Chief Patrol Agent Aaron Heitke said in the release. "I am proud to say that our Border Patrol agents here in San Diego Sector are responsible for over 50% of all the fentanyl seized by the U.S. Border Patrol this fiscal year."

CNN has reached out to the DEA for comment.

Fentanyl typically makes up a small percentage of the agency's annual drug seizures at the southwest border, CBP data shows. The vast majority of seizures in the region are of marijuana, methamphetamine and cocaine, according to annual data.

Last week, the CBP agents in Texas seized almost 90 pounds of cocaine, the agency announced. Packages of the narcotic were found in a Freightliner tractor and estimated to have an estimated street value of $691,560.

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