A complex operation to remove a suspected World War II bomb in Darwin Harbour has been suspended after an elite navy dive team failed to locate it over the weekend.
The potential weapon, believed to be a 60 to 80 centimetre mortar shell dropped during Japanese raids was found by commercial divers during a survey of the proposed Darwin Ship Lift site last week.
Members of the Royal Australian Navy's specialist clearance diving team arrived in Darwin on Friday to relocate and recover the suspected shell.
But despite an "extensive search" over Saturday and Sunday, a Defence spokesman said the five-member team had been unable to find it.
"While the location marker left by the commercial divers who found the suspected UXO has been found, the ordnance has not," the spokesman said in a statement.
"On Sunday, 25 September the conduct of the search was handed back to commercial divers."
The statement said the navy dive team would remain in Darwin for "a number of days" to provide expertise if commercial divers found the ordnance again.
Commercial divers returned to surveying the site today.
A 250 metre exclusion zone set up around the item last week will remain in place for the time being, however it is "constantly being reviewed", a Department of Planning, Infrastructure and Logistics spokeswoman said.
David Ciaravolo, chief executive of recreational fishing peak body the Amateur Fishermen's Association of the Northern Territory, said the news was disappointing for fishers who usually used the area, but it was important the risk was "properly addressed".
"It's probably to be expected that it's going to be quite a complex operation," he told ABC Radio Darwin this morning.
"I think there was no timeline initially forecast for how long it would take, and [when] we engaged with the government, we were told it'll be closed for as long as it takes.
"So it's disappointing, but not probably surprising, that it hasn't been resolved just yet."
He also said challenging conditions in the harbour could have made the search particularly difficult.
"The harbour is subject to pretty extreme currents ... [and] you can be over a spot, but you can't get GPS until you're on the surface," he said.
"Visibility in the harbour can also be really difficult."
