LOS ANGELES (AP) — Ten people have been arrested so far after last week’s federal raid on 17 Southern California auto parts stores accused of distributing nitrous oxide for use as a recreational drug.

Food and Drug Administration agents shut down the stores in Los Angeles, Riverside Orange counties March 22 and arrested four people on misdemeanor charges of violating the federal Food, Drug and Cosmetic Act by misbranding a drug.

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Five others were arrested on weapons or narcotics charges, and a 16-year-old boy holding a “nozz” party was arrested for furnishing nitrous oxide to a minor, Los Angeles County sheriff’s spokesman Mike Parker said Friday.

Authorities said they seized more than 640 nitrous oxide tanks with an estimated street value of $20 million. They also seized 13 guns, including four stolen weapons, four assault weapons, high-capacity magazines and ammunition including armor-piercing rounds, Parker said.

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The raids were the result of a 15-month joint investigation dubbed “No Laughing Matter” by the FDA and the Sheriff’s Department. Authorities said it was the largest action ever launched against the illegal recreational use of nitrous oxide in the United States, and more arrests could be coming.

Nitrous oxide is legally used by dentists for anesthesia, to pressurize whipped cream canisters and to speed up race cars. But authorities say its illegal use has spurred fatal car accidents, rapes and teen deaths — all in the name of a temporary high.

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