The US military conducted 50 highly-classified tests of biological and chemical agents in the 1960s and 1970s to find out how they would act in different environments and weather conditions, the US defense department has disclosed.

The announcement yesterday capped a nearly three-year investigation into so-called "Project 112" and its outgrowth, "Project Shad," which were carried out over land and sea in various parts of the world - from the Marshall Islands to Panama, Canada and Britain - and involved as many as 5 842 US troops.

"We were very fortunate to find the progress reports," said lead Pentagon investigator Dee Dodson Morris, who made clear the project was so thoroughly classified that its scope was not known even to top department officials.

"They served as a valuable template and a roadmap of sorts".

The origins of the programme go back to 1961, when defense secretary Robert McNamara ordered a series of tests to see if chemical and biological weapons could be effective.

As part of that initiative dubbed "Project 112," the Joint Chiefs of Staff set up a centre at Fort Douglas, Utah, in June 1962 to manage the programme.

It took the military nearly six months to have the tests up and running.

In January 1963, the Navy launched off the coast of the Hawaiian island of Oahu a series of tests, code-named "Eager Belle", were designed to determine whether aerosols containing a biological agent could penetrate US warships.

During the experiment a Navy ship was sprayed from a tugboat with the non-lethal bacteria Bacillus globigii "to evaluate the effectiveness of selected protective devices".

With the Cold War in full swing, US war planners also wanted to know how deadly nerve agents such as Sarin and VX would behave in subzero temperatures dominant in winter time in much of the former Soviet Union.

Hence, experiment "Whistle Down" conducted between December 1962 and February 1963 at Fort Greely, Alaska.

As part of these tests several Sarin and VX-filled artillery shells, rockets and land mines were remotely detonated near the Gerstle River.

To see how weapons of mass destruction could penetrate the jungle canopy, the Pentagon went in early 1963 to the Panama Canal Zone to hold exercise "Big Jack".

It involved aircraft spraying simulant agents over the Fort Sherman military reservation.

Britain and Canada were chosen for a series of tests code-named "Rapid Tan" whose goal was to determine how long the nerve agents Tabun, Sarin, Soman and VX would maintain their killing capabilities in a wooded terrain and open grassland.

Under a shroud of secrecy, the deadly weapons were sprayed several times during 1967 and 1968 from crop dusters, or delivered by howitzer shells, over the military test sites in Porton Down, Britain, and Ralston, Canada.

"Blue Tango" involved 20 experiments with spraying live E.coli bacteria that could sometimes be deadly to humans over the Island of Hawaii between January and March of 1968.

The Pentagon experimented even with releases of bacteria into the ocean to see if biological weapons could be effectively delivered by a submarine.

As part of a 1968 series of tests dubbed "Folded Arrow," the submarine USS Carbonero dumped Bacillus globigii into the ocean off Oahu "to demonstrate the submarine weapons system capability to carry out an effective biological attack against an island complex and a naval port facility".

The purpose of the Pentagon probe was to determine how many people could have been affected by the experiments to handle possible health-related claims.

"I am pleased that our investigators were able to bring closure to this in-depth investigation, and by replacing speculation and uncertainty with fact, to offer the veterans of these tests some much deserved peace of mind," Assistant Secretary of Defense William Winkenwerder said in a statement. - Sapa-AFP.