And on Friday, Norfolk Police revealed there had been an "unplanned" detonation.
No injuries were reported and police said all army and emergency service personnel were accounted for.
Army specialists had been cutting the bomb using a technique that creates a slow burn of the explosives, police said. Workers began attempting to cut into the bomb on Thursday.
Police captured video of the explosion via their drone.
"This has been a painstakingly long process but public safety and that of the people involved in the operation has been at the heart of decision-making," Norfolk Constabulary's Assistant Chief Constable Nick Davison said in a statement.
"This was the final phase of a delicate operation which has caused much disruption in the town, but we're hopeful this could be resolved soon, and that cordons can be lifted, if everything goes to plan," he continued.
A spokesperson for Cadent, which manages the local gas mains network, said the company has conducted a "close inspection of our pipes in the vicinity," according to Sky News.
"There is no indication that the blast has caused damage to our assets and gas continues to flow safely," the spokesperson said.