Beware of the mussels?

Saw item in today's S China Morning Post, mentioning that 13 people had been taken to hospital with apparent food poisoning, after eating in a Cheung Chau restaurant.

Read this over meal at a Cheung Chau restaurant, and asked guy there for info. He figured the problem was with mussels - said they've very dirty on Cheung Chau. Wouldn't surprise me: mussels are filter feeders, and can accumulate nasty stuff, including as can grow in some rather dirty water - and there's plenty of dirty water around Hong Kong!