Moscow, Apr 23 (IANS/RIA Novosti): Police in Moscow have shut down an illegal casino that was operating on the premises of a former sugar refinery, the interior ministry said.

Over 20 gamblers were detained in the casino, which housed several poker tables and 50 slot machines.

Police seized a large number of playing chips and stacks of cards, as well as computer hard drives containing information about gambling operations, a statement said.

The casino owners were making an estimated 10 million rubles (around $300,000) a day, police said.

The ministry did not say when the raid took place.

The underground club was located in a part of the factory that was hard to access, behind steel doors of the kind used in bank vaults.

Information about how to access the gambling den was provided via text message to regular clients.

Last week, Moscow police shut down an illegal casino operating on the premises of a state university.

The casino, located at Moscow State University of Instrument Engineering and Informatics, had a daily income of three to five million rubles ($96,700-$161,000) a day, police said.

Since July 2009, gambling in Russia has only been allowed in four specially allotted zones, driving much of the business underground into a thriving black market.