More than 30 people attending a birthday party last Saturday fell ill after eating the catered food, said the host of the event.
The caterer has now been suspended while the National Environment Agency (NEA) investigates the incident.
According to Lianhe Wanbao, two among the 33 taken ill had to be hospitalised after they had sampled the buffet ordered from Kuisine Catering last Saturday.
The party host, a nail salon owner who wanted to be known only as Madam Tan, said she had held the event at her home in Pasir Ris for her child's seventh birthday. A total of 34 people attended it, including her family of four.
But things went awry after the celebrations.
"My husband started vomiting and having diarrhoea after 3am, and (the rest of the family) also started having the same symptoms the next afternoon," she said.
"We felt that something was not right, so we called the party guests and found out that everyone had the same symptoms of food poisoning, from an 85-year-old elderly guest to a kid of three years."
Madam Tan, 48, said her friends and relatives later went to hospitals and clinics for treatment, and doctors confirmed they had food poisoning. She said her husband and daughter's boyfriend ran high fevers and were admitted to hospital to be put on a drip.
Food for 30 was ordered from Kuisine, and a birthday cake was also served. The one person at the party who did not fall ill had eaten only the cake and nothing else, said Madam Tan.
A spokesman for Kuisine Catering said the company had fully refunded Madam Tan's order.
He said the caterer had earned an A grade from the NEA for its overall hygiene "for many years", and that food served during the event was "general buffet food".
"We also do not want this to happen and we are also not sure what exactly happened. We are hoping that the relevant authorities can expedite their findings and inform us of the conclusion, so that we can really let our customer know," he said in a press statement.
NEA guidelines require food handlers for buffet and catered meals to have completed training and be registered with the agency.
Chilled and frozen food should be stored at appropriate temperatures, and caterers should cook and prepare food as close to the delivery time as possible. Catered food must be time-stamped, with the displayed "consume by" time to be no later than four hours after the food is cooked or made to a ready-to-eat state.
The NEA, Ministry of Health and Agri-Food and Veterinary Authority are investigating the case.