An investigation has been launched into whether contaminated raw sea urchins are behind a recent spate of food poisonings involving Japanese restaurant and noodle shop chains.

The Centre for Health Protection said most of the affected people had eaten sea urchin before they fell ill. So far 66 people in 24 groups have been sick after eating at the restaurant's four outlets in Hung Hom, Causeway Bay and Quarry Bay between June 27 and July 3.

One of the patients tested positive for Vibrio parahaemolyticus, a bacteria usually found in seafood. Of the 23 males and 43 females, aged seven to 75, two have been hospitalised and discharged.

Meanwhile, two more food poisoning reports involving seven people who ate at the noodle shop chain's outlets in Olympian City and Heng Fa Chuen have been received, and most had eaten raw sea urchin.

The two men and five women, aged eight to 57, developed diarrhoea, vomiting, abdominal pain, nausea and fever after eating at the outlets on July 2 and 3. Two sought treatment at public hospitals and two consulted general practitioners. Their symptoms were generally mild and none required hospitalisation.

Initial investigations have found that the raw sea urchins were supplied by the same supplier, Ho's Brother's Sea Food Company. The supplier has been ordered to stop distributing the product.