Chernobyl: Huge section of roof covering nuclear reactor which exploded in 1986 collapses under the weight of snow 600sqm section caved in over turbine hall of crippled power station Fifty workers evacuated from the site as a precaution Officials immediately deny there was any threat of a radiation leak Greenpeace expert says it is 'an alarming signal' for the safety of the plant Death toll from blast in April 1986 could reach hundreds of thousands A huge section of roofing covering part of the defunct nuclear power plant at Chernobyl has collapsed under the weight of snow. Officials immediately denied any threat of radiation even though the accident involved a cover on part of the workings of Reactor Number 4 which exploded in 1986 in the world's worst atomic disaster. There are no safety hazards. The radiation situation at the plant and in the exclusion zone is normal. No one was hurt,' said the administration at the former Soviet plant. Worrying: A large section of roofing (circled) covering part of the defunct nuclear power plant at Chernobyl has collapsed under the weight of snow Playing it down: Officials immediately denied any threat of radiation even though it involved a cover on part of the workings of Reactor Number 4 which exploded in 1986 in one of the world's worst atomic disasters No threat: The sarcophagus structure covering the reactor, which is in the process of being replaced, was not hit by the roof collapse which was in an adjacent part of the plant It cannot affect the radiation background. The situation is not even classified as an emergency,' said Dmitry Bobro, the first deputy director of the state agency for the management of the Chernobyl exclusion zone, a no-man's land surrounding the power station. The sarcophagus structure covering the reactor, which is in the process of being replaced, was not hit by the roof collapse which was in an adjacent part of the plant. The area of the collapse was about 600 square metres (6,456 square feet) in the turbine hall of the disused power station, which is in modern-day Ukraine. 'There is no threat to the lives or health of the population,' said a statement from Russia's Emergencies Ministry, echoing Ukrainian assurances. 'The snow piling up on the roof of the turbine hall caused part of the roof and some of the new panels to collapse,' he said. As for the state of the Shelter facility, it is stable. It will remain the way it has been. There are no radiation consequences of this emergency. The main consequence is that all those holes will have to be patched up. Containment: Work was already under way to replace the sarcophagus, which is in danger of cracking Meltdown: The Chernobyl disaster occurred on April 26, 1986, when one of its four nuclear reactors exploded The blast on April 26, 1986, spewed a cloud of radioactive fallout over much of Europe and forced hundreds of thousands from their homes in Ukraine, Belarus and western Russia. Scientists are deeply divided on how many have died as a result of the explosion, which released about 400 times more radiation than the U.S. atomic bomb dropped over Hiroshima. The United Nations set the death toll at 4,000, but non-governmental groups have suggested it could reach tens or even hundreds of thousands. The explosion occurred after engineers at No. 4 reactor conducted a botched experiment to see whether the cooling pump system could still function if the auxiliary power supply failed. Today, the 19-mile 'zone of alienation' is largely uninhabited, but has become a popular tourist attraction. A new giant arch-shaped confinement is currently being constructed over the old sarcophagus, which is in danger of cracking. The construction of the new shelter was not affected by the accident, said Anton Usov, spokesman for the European Bank for Reconstruction and Development, which runs the $2 billion project co-sponsored by the bank and international donors. 'The old shelter was not affected, the new safe confinement was not affected either,' Usov said. Vinci and Bouygues, two French construction companies who are contracted to work on building the new confinement, said they had evacuated about 80 workers as a precaution. They had not returned as of Wednesday. Chernobyl plant spokeswoman Maya Rudenko called that a standard measure of precaution and said the workers are expected to return as soon as an investigation into the accident is completed and the roof is reinforced in order to prevent water from getting inside. She also added that Ukrainian workers at the plant have not been evacuated or ordered to implement any additional safety measures: 'We are not wearing face masks, we have not been evacuated, which is what would have happened had there been danger.' However, the collapse and the failure to remove heavy snow from the roof will not inspire confidence in safety measures at the plant, which continues to present a substantial threat of radioactive pollution to Europe. 'Even if the radiation level has not changed, it's still an alarming signal,' Vladimir Chuprov, head of the energy program at Greenpeace Russia, said, according to the Interfax news agency. If the panels in the turbine hall have collapsed, then in principle there is no guarantee that the sarcophagus, built in 1986, will not start falling apart in the near future. The Chernobyl disaster took place on 26 April 1986, when one of its four nuclear reactors exploded. The Soviet leadership was slow to admit the scale of the accident and order an evacuation, causing unnecessary radioactive damage to workers and people upwind from the plant. Radioactive contamination spread as far as Britain and northern Sweden.