A Mongkok restaurant was ordered to close last night after cholera was found in a water sample taken from its fish tank. The Manchu Chinese Seafood Hotpot Restaurant, in the basement of New Wish Mansion, Nathan Road, operates 24 hours a day and seats 300. The Food and Environmental Hygiene Department took environmental swabs and food and water samples from the restaurant this week after a 50-year-old man in Fanling contracted cholera earlier this month. Test results yesterday confirmed the presence of Vibrio cholerae in a water sample, although the strain was different from that which caused the cholera case. 'The restaurant will remain closed until disinfection is completed to our satisfaction,' a department spokesman said. 'It will be reopened when we are satisfied with the overall hygienic conditions of the premises. 'We have tracked down the fish tank water supplier and are tracing the source of the water.' The spokesman said the department had stepped up inspection since June of food premises with fish tanks installed. 'Of the 1,500 such food premises, we have inspected over 1,300 of them to check that their fish tanks are connected to filtration and disinfection facilities, and collected water samples for testing of Vibrio cholerae.' The department has also put up warning signs at a number of polluted seawater spots and has stepped up surveillance to deter operators of food premises from drawing water from those spots. The department said 31 restaurants were found to be selling raw seafood in unhygienic conditions during an inspection blitz aimed at stamping out cholera earlier this week. Food inspections were made after raw shrimps, crabs and fish sold in restaurants were implicated in four cholera cases this month. Restaurant owners illegally selling food eaten raw are liable to a maximum fine of $50,000 and six months' jail. There have been 17 cholera cases recorded so far this year. Of these, only one was classified as an imported case. There were 12 cholera cases last year, 18 in 1999 and 71 in 1998.