Health authorities are investigating imported frozen berries after four people fell ill with the vomiting virus hepatitis A.
Peter Thomson, of the Ministry for Primary Industries, said "Our investigations to date have not revealed a specific cause, but there is an association with consuming frozen berries.
"Recent outbreaks in other countries also suggest this link."
In February, the ministry said it was monitoring frozen berry imports after a recall of frozen mixed berries in Australia prompted by cases of hepatitis A.
This evening, the ministry's director-general has issued a statement warning of a "potential risk associated with imported frozen berries" following the four cases "thought to be linked to packaged imported frozen berries".