"There's a real risk of detonation during the process of dealing with the bomb."

That is the message from Great Yarmouth's head of police superintendent Nathan Clark, as he urges residents to stay safe during the defusing of a riverside bomb.

A 250kg unexploded bomb, believed to be from the Second World War, was found during dredging work in the River Yare by Bollard Quay in Southtown on Tuesday.

Great Yarmouth Mercury: The exclusion zone by Bollard Quay in Southtown. Bomb disposal experts are currently working at the site to deal with the unexploded device.The exclusion zone by Bollard Quay in Southtown. Bomb disposal experts are currently working at the site to deal with the unexploded device. (Image: Denise Bradley)

Since then, road closures have been set up within a 400m radius of the area close to the Third River Crossing. Residents in the surrounding streets have also been strongly advised to evacuate their homes as bomb disposal experts from an army base in Colchester continue to deal with the bomb as safely as possible.

This morning (February 8), 400 tonnes of sand was brought to Bollard Quay to help construct a blast barrier around the bomb.

Supt Clark said: "The sand bank defence is currently being built around the device, and the military would like to get this done within the hours of daylight. The work is still ongoing, and they are on target.

"Once that's done, the real work will begin."

Great Yarmouth Mercury: Army bomb experts dealing with the unexploded device by the River Yare at Great Yarmouth.Army bomb experts dealing with the unexploded device by the River Yare at Great Yarmouth. (Image: Denise Bradley)

Supt Clark said the team will cut through the bomb to remove the detonator. This process could take up to 18 hours.

"This could be a very long process," Supt Clark said.

"And the military has to get up close and personal with the device. There's no way around it.

"But that is the nature of their work, and they operate within that area of risk.

"It's a very complicated process, but essentially the experts will cut through the bomb for a safe detonation. The remainder of the device will then be detonated out at sea."

Great Yarmouth Mercury: A sand wall has been built around the bomb (Image: Oliv3r Drone Photography)A sand wall has been built around the bomb (Image: Oliv3r Drone Photography) (Image: Oliv3r Drone Photography)

However, the superintendent said there is still a risk the device could detonate in full at any point during the process.

Residents within the exclusion zone are advised to evacuate their homes for a second night.

Supt Clark said: "Any controlled explosion will likely cause damage. It's a very risky process to take.

"The immediate threat is the blast.

"If the bomb does goes off, anyone nearby could be hit by shrapnel and there is extreme risk of injury to anyone behind glass."

Supt Clark said there are also other risks to infrastructure in the area, including that belonging to the Third River Crossing, which is still under construction.

"It could be a catastrophe if all that work was stalled," he said.

"There are a host of risks to manage and that is why we are advising caution."

Great Yarmouth Mercury: Supt Nathan Clark across the River Yare from where the army bomb experts are dealing with the unexploded device at Great Yarmouth.Supt Nathan Clark across the River Yare from where the army bomb experts are dealing with the unexploded device at Great Yarmouth. (Image: Denise Bradley)

Supt Clark advised the public: "Stay safe. Don't take risks.

"Stay away from the site because there is a real risk of its detonation during the process.

"If you are within 200m of the exclusion zone and are instructed to leave the house by emergency services, you absolutely must do so. If you are within the 400m range, you are also advised to evacuate.

"We cannot maintain safety unless you follow our advice."

Great Yarmouth Mercury: The bomb by Bollards Quay, Great Yarmouth. (Image - Oliv3r Drone Photography).The bomb by Bollards Quay, Great Yarmouth. (Image - Oliv3r Drone Photography). (Image: Oliv3rDrone Photography)

Supt Clark said that later today, police may have to enforce people leaving their homes if they live within 200m.

The rest centres will remain open at St Georges Theatre in King Street, Great Yarmouth, and Mesh - Shrublands Youth and Adult Centre in Magdalen Way, Gorleston.

An emergency helpline has been set up for people who require assistance with evacuation from the exclusion zone. This helpline is 01493 330369 and should not be used for general advice.

People concerned about their health or prescriptions left at home are being advised to call 111 for support.