Seafood lovers have been warned to be careful with raw mussels after an outbreak of food poisoning.

New Zealand Food Safety announced on Friday it’s seen an uptick in the number of people contracting food poisoning from Vibrio parahaemolyticus.

Most of the people who got sick ate commercial grown mussels harvested in Coromandel.

“It is possible that the strain of vibrio parahaemolyticus is unusually aggressive, which may mean that even low numbers could cause illness,” NZ food safety director of regulation Paul Dansted said.

“Additional testing of mussels and the waters that they are being grown in is also underway to help us understand why this has happened.

“The mussels at the centre of the outbreak were all bought in their raw state, in the shell. They are not the mussels that can be bought in plastic pottles. Those mussels are cooked and marinated and are not affected.”

NZ Food Safety says people need to be careful when cooking mussels and heat them above 65C. It’s also advised to wash hands after handling shellfish, and avoid cross-contamination between raw and cooked shellfish.