Thieves stole a number of firearms from a South Island house while the occupants were evacuated due to yesterday's tsunami warning.

Police said the firearms, some of them antiques were stolen from an address in Riwaka in the Nelson area at about 7.30am.

"For someone to take advantage of others at a time like this is a deplorable act," said Nelson Bays Area Commander Inspector Mathew Arnold-Kelly.

"We do not want these firearms to fall into the wrong hands. Police have launched an investigation as a matter of priority".

"We are appealing for members of the public to help us to recover these weapons. Any information, no matter how small, could assist us in resolving this crime."

Arnold-Kelly said information could include sightings of individuals behaving suspiciously or collectors being approached to buy the firearms

Police are keen to speak to a male Eurpoean in his mid to late 30s wearing a grey hoodie and black pants who was riding a red push bike in the area at the time.

Anyone with any information is encouraged to contact Nelson Bays Police on 03 546 3840.