UNION CITY (CBS SF) — Acting on an anonymous tip, Union City police detectives have busted up a massive marijuana operation, uncovering 20 illegal grow rooms in the San Francisco Bay Area and seizing approximately 15,000 pot plants with a street value of about $27.5 million.

Union City police said that in June its Special Services Unit received an anonymous tip about an illegal marijuana grow and opened an investigation.

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Over the next several months, SSU detectives secured a number of search warrants for the locations allegedly associated with the operation and the seizure of bank accounts.

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Using the search warrants, detectives uncovered and found an illegal marijuana cultivation operation consisting of 20 grow rooms and associated equipment.

They seized approximately 15,000 marijuana plants with a street value of about $27.5 million. Also seized during the operation was $22,000 in cash, items used for cultivation and a bank account with approximately $250,000 in illicit funds.

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There was no immediate details released on arrests made in the case.