BHP Billiton says third party surveys carried out at its Precinct 3 workers' camp site in Port Hedland confirm there were no "intact" unexploded bombs remaining from World War II.
The assurance came after pieces of what were thought to be from a Japanese bomb were found at the site by contractors.
A BHP spokesman said the company was aware that "fragments, not intact unexploded ordnance", had been unearthed in the vicinity of the proposed 2000-man camp next to Port Hedland airport.
The company said FESA, the responsible authority with respect to unexploded ordnance, had previously identified the possibility that the site could be impacted by unexploded bombs but the risk of finding them intact was minimal.
The artefacts were handed to _The West Australian _anonymously after being found by a crew from Eastern Contracting, which is carrying out preliminary site works for Decmil Australia. Decmil won the $94 million contract to build the BHP camp earlier this year.
Retired Royal Australian Air Force armourer Bob Alford said the pieces appeared to be from bombs dropped on Port Hedland airfield during the first of three Japanese raids on the Pilbara town.
The July 30, 1942, strike killed Private John Adams, believed to have been the only man born and enlisted in WA to be killed by enemy action in the State throughout World War II.
Mr Alford, who now lives in Thailand, said the most distinctive piece of the four found appeared to be the nose section of a demolition bomb, complete with the fuse well in the centre. "It certainly looks like (a bomb). I can see the fuse well in that piece," he said.
Port Hedland RSL president Val Middleton said if the pieces were confirmed to be from a Japanese bomb then the discovery was hugely significant."It's a memento for this town that should be treasured," he said.
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