OAKLAND, Calif. (AP) — Federal agents have raided a San Francisco Bay area medical marijuana training school at the heart of California’s pot legalization movement.

The doors to Oaksterdam University in downtown Oakland were blocked Monday morning by U.S. marshals.

Agents from the U.S. Drug Enforcement Administration carted trash bags of unknown materials out of the school to a waiting van.

About a dozen protesters out front held signs demanding an end to federal crackdowns on medical marijuana.

Oaksterdam University was founded by Richard Lee, the main backer of the California ballot measure defeated in 2010 that would have legalized marijuana in the state for recreational use.

The school is in an Oakland neighborhood that has also been home to several medical marijuana dispensaries, including one founded by Lee.