LOS ANGELES (AP) — Federal prosecutors have sent dozens of letters warning medical marijuana shops in Los Angeles and Long Beach to shut down or risk potential criminal or civil action.

Authorities say more than 100 pot clinics across Los Angeles County received the letters Tuesday. Lawsuits also were filed against two property owners in Long Beach, telling them it's illegal to allow pot sales in buildings they own.

California's federal prosecutors launched a coordinated crackdown on the state's medical marijuana industry in 2011 by threatening landlords with property forfeiture. Since then, many of the 625 pot shops targeted in the seven-county Central District of California have closed.

California was the first state to legalize marijuana for medical use when voters passed Proposition 215 in 1996, but it remains illegal under federal law.

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