The seizure included concentrated cannabis oil, hashish and marijuana. Also seized were an AR15 rifle, three handguns and $150,000 in cash.
The total value of items seized was estimated at $20 million, according to Capt. Marc Reina of the Central Area.
The arrest was made after someone called police about suspicious activity at an unmarked building in the 800 block of South San Julian Street.
Four Los Angeles residents were arrested at the downtown operation, one for operating the unlicensed drug business and three for working there.
Police note that while marijuana has been legalized in California, officials want to make sure it is being sold by a licensed business and that the product is from a responsible and regulated source.
Officials believe the operation was selling drugs, including designer cannabis products, wholesale to local dispensaries