Emergency services have so far been unable to recover the bodies of two men killed in an explosion at an industrial plant due to the presence of chemicals.
Two men, one aged in his 50s and one in his 20s, were killed shortly after 9am today after the blast in the fabrication workshop at digger bucket manufacturer Harford Attachments in Spar Road, Norwich.
Both were employees and nobody else was hurt in the incident.
Workers raised the alarm after hearing a loud noise inside the building. They rushed to the scene but were unable to help the victims.
Witnesses reported seeing smoke billowing from the building.
Superintendent Dave Marshall, from Norfolk Police, said: "We are carrying out an investigation alongside the Health and Safety Executive and the fire service.
"We need to make sure the scene is safe and so far we have been unable to recover the men's bodies because of the high level of chemicals in the air.
"The families of the men have been informed and specialist officers are supporting them. I would like to offer my condolences to them at this time."
Scott Norman, from Norfolk Fire and Rescue Service, said crews had arrived at 9.06am.
He added: "When we arrived smoke was billowing from a large building, our crew entered the property and located the room which the fire was in.
"We then extinguished the fire but unfortunately two people died at the scene."
A helicopter from the East Anglian Air Ambulance was also deployed, although the crew did not include the Duke of Cambridge, who began work with the charity today.
The estate was largely shut off to the public while the incident was dealt with.
A cordon is expected to remain in place on Spar Road overnight.