No specific "event or food premises or stall" has been found to be the source of last month's outbreak of gastroenteritis cases in the Owen Road area, said the authorities, who yesterday declared it over.

In a joint statement, the National Environment Agency (NEA), Health Ministry, Agri-Food and Veterinary Authority and national water agency PUB said the number of cases has now declined to usual levels and there have not been further hospital admissions linked to the outbreak.

To date, 180 cases have been linked to the outbreak, which led to a two-day closure of Pek Kio Market and Food Centre for cleaning and disinfection. Seventeen patients were admitted to hospital.

But it is still not quite business as usual at the market and food centre, the epicentre of the infection.

It was closed for a thorough cleaning after investigations found it had been patronised by many of those who later fell sick with vomiting and diarrhoea.

This was undertaken as a precautionary measure even though all food, water and environmental samples collected from the area tested negative for the virus responsible for the illness.

NEA said it would continue to monitor the centre to ensure that the stallholders observe hygienic practices and that the toilets are maintained and cleaned.

Market researcher Anna Ow, 54, who has lived nearby since 2007, said she noticed that the crowds had declined by about one-third.

She said: "I would still go to the market, but because some patients have gone to the hospital, I have to be more careful about what I eat."

Still, the stall owners who cooperated and participated in the cleanup are optimistic.

"We have always maintained a clean stall and I hope the customers will come back slowly," said Ms Chen Chun Ruo, 45, of Sin Kee Nasi Lemak Economical Bee Hoon Mee.

The illness, known as rotavirus gastroenteritis or more commonly gastric flu, is a bowel infection that usually afflicts children. It is easily transmitted from person to person.

The risk of infection can be minimised by observing good personal hygiene such as washing hands and using separate utensils for sharing food, said the authorities.

Meanwhile, customers at the food centre and market have been supportive, if slightly cautious.

Said Mr Marcus Lin Weijian, 55, a manager at an export company: "The stalls were pretty clean even before the outbreak.

"This market is actually cleaner than other markets in Singapore."

He added: "It takes some time for people to overcome their fear and come back."