The Ministry of Primary Industries has launched a major testing programme on frozen, imported berries.

It says it's been alerted to four cases of Hepatitis A linked to people eating frozens that were packaged overseas. The ministry is warning people to cook or boil berries before eating them.

MPI food director Peter Thomson said officials are doing additional testing on all frozen berries coming in at the border.

"We'll also be testing any imported frozen berries being held in stock by importers currently."

The warning does not apply to New Zealand berries, whether they are fresh or frozen.

Peter Thomson said the ministry has investigated local berries, and have found they are still safe to eat.

"There's no evidence that domestically produced berries, fresh or frozen, have any heightened level of risk."

Some Australian frozen berry products were recalled earlier this year following a Hepatitis A scare.