The US Food and Drug Administration (FDA) is trying to account for the whereabouts of 282 boxes of frozen fish, which were labelled as monkfish but that may contain the deadly poison tetrodotoxin, found in puffer fish.

The problem came to light after two people in the Chicago area were admitted to hospital with acute symptoms of tetrodotoxin poisoning. The toxin paralyses muscles, including the heart in fatal cases. It is not broken down by cooking or freezing.

The consignment was imported from China by Californian company Hong Chang Corp last year. The frozen fish was sold to wholesalers and the majority of the batch has been resold to restaurants, retailers and cash and carry stores across Illinois, California and Hawaii.

The FDA has started checking all the data from the Chinese supplier concerned.