Shanghai authorities vowed yesterday to implement stricter measures to guard against Sars, even though the city's official tally of cases remains low. Last week, Shanghai announced sweeping rules to fight the virus. But some of the rules were vague and foreign diplomats have pressed for an explanation of how they will be interpreted. 'The implementation is weak. We want to carry them out more strictly,' said deputy secretary-general of the Shanghai government, Xue Peijian. Government officials told diplomats that the measures would include enforcement of 14-day quarantine periods for residents and travellers coming from infected areas. Residents would be confined to their homes, and visitors to their hotels. Other steps include quarantining schools and companies which have at least two Sars cases. Shanghai had ordered universities to reduce class sizes to less than 30 and to try to keep students on campus to avoid the spread of the virus, the officials said. The Shanghai education commission had already announced that universities would give students just one day off for the Labour Day holiday today. Officials said Shanghai had set up traffic checkpoints to screen people coming into the city, taken people's temperatures and ordered them to fill in health declaration forms. Witnesses said some checkpoints were only screening passengers in vehicles without Shanghai licence plates. As of yesterday, Shanghai had two confirmed cases and 12 suspected ones, including two US citizens, a French national and a person from Hong Kong, the health bureau said. The French citizen was a four-year-old girl who visited Beijing with her family, diplomats said. An official from the World Health Organisation, which recently inspected Shanghai, said this week that the number of cases in the city was likely to be higher than the official count though the team found no systematic under-reporting. WHO team leader James Maguire said: 'That doesn't mean that we're confirming there are only two cases. 'There's certainly a very good possibility of more cases, perhaps 10 or so.'