A United States reporter says the New Zealand Government would have been told if New Zealand is one of five unidentified countries that were dumping grounds for US chemical weapons, after World War Two.

John Bull, a reporter at The Daily Press in Newport News, Virginia, has unearthed a restricted memo from 1944 which reveals that American chemical weapons were stored here during the war.

But he says he found no evidence they were ever returned.

Dumping surplus weapons at sea was standard practice at the time - and mustard agent has previously been dredged up off Australia.

Eleven countries have been identified as being dumping grounds for the weapons like nerve and mustard gas, but five sites remain undisclosed to the public.

Mr Bull says those countries, which could include New Zealand, were notified of the predicament by the US Government.

A spokesperson for the Minister of Defence says officials are checking to see if New Zealand is one of those countries, but says there does not appear to have ever been any notification from the US government.