New Zealand Government researchers have combed the United States Government national archives for information on chemical weapons dumped off the New Zealand coast.

At the end of World War 2, the US Army secretly dumped millions of kilograms of chemical weapons off New Zealand and a dozen other countries.

The dumpings took place as the US was short of space in home-based munitions depots.

US-made weapons litter 30 sites off New Zealand, Australia, New Caledonia, the Philippines, Italy, France, India, Pakistan, Japan, Denmark and Norway, a report by the chemical weapon historical research and response team at the Aberdeen Proving Ground in Maryland, US, said.

The Daily Press of Newport News, Virginia, reported that an August 24, 1944, memo -- classified at the time as "restricted" -- revealed the US kept stockpiles of chemical weapons in New Zealand during World War 2.

Chemical weapons were also kept in China, the former Soviet Union and unidentified "Latin American countries", one of which was understood to be Panama.

The US Army has said it told the governments of those five unidentified countries in recent years of the dangers lurking off their coasts.

It was asked by those governments not to release the information to the public.

Two years ago, New Zealand Government researchers turned up at the US National Archives, seeking information on chemical weapons ocean dump sites, US archivist Tim Nenninger told the newspaper.

The US Army has since admitted secretly dumping at least 29,000 tonnes of chemical warfare agents as well as more than 400,000 mustard gas-filled bombs and rockets off the US coastline.

Much more than was said to have been dumped off the coasts of other countries, the Daily Press reported.

But the US Army is missing years of records on where it secretly dumped surplus chemical weapons from the close of World War 2 until 1970.

In 1983, an Australian fishing trawler snagged a one-tonne steel container of mustard agent dumped off the coast of Cape Moreton in Queensland by the US.

No one was injured.

It happened in relatively shallow water not far from where the US Army admitted it had dumped an estimated 30,000 tonnes of mustard agent and toxic Lewisite in drums, and in hundreds of thousands of chemical-filled artillery shells.

The gas from mustard agent and Lewisite are powerful irritants which cause blisters.

In 2003, the Australian government created an in-depth report on what it calls chemical warfare agent dumps, identifying exact latitudes and longitudes of US and Australian-created chemical weapons dumps. The information was released to the public.