Army bomb disposal experts have abandoned attempts to cut into a huge wartime bomb which has forced the evacuation of hundreds of homes, and are now reverting to what they say is the "only option" open to them.
An operation to cut into the casing of the 250kg device on a quayside in Great Yarmouth in Norfolk began on Thursday but was halted after water began to destabilise sand barriers which had been built up around it.
Late on Friday they said they had been forced to change their tactics, and would now use a technique that creates a slow burn of the explosives.
That operation will create lots of white smoke they said, and a "large risk of a full explosion being detonated", said Norfolk Police's Supt Nathan Clark.
"It's the only option, as the integrity of the [sand defence] structure has to be maintained," he told ITV News Anglia.
"If we lose that structure then we lose all the protection that we have put in place."
Police warned that "as with other options, it does carry a risk of an unintended detonation" but said the approach had been assessed by experts and was "seen as the best course of action".
Supt Clark said any explosion would be "an extremely large blast", risking injuries, shattered windows and damage to buildings within 200m of the site.
He said the new approach was "not the preferred solution".
Police have moved to reassure residents that the smoke is not harmful to human health.
"Once the slow burn concludes a period of time is required for the location to cool," said a spokesman. "The army specialists will then assess whether it has been successful and inform local services of the outcome and whether it has been successful or not."
If the operation is successful, cordons are expected to be reduced or fully lifted.
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