A fire raging dangerously close to Russia’s main nuclear research centre expanded yesterday as firefighters battled to cut back hundreds of blazes across the country.

The emergencies ministry said that over 500 fires covering just under 65,000 hectares of land were still ablaze across Russia, down 15,000 hectares from the day earlier, in a crisis that has already left 54 dead.

Russian has sent thousands of firefighters to a nature reserve near the country’s top nuclear research centre in Sarov, a town still closed to foreigners as in Soviet times, and officials warned a fire was gaining in area.

“The fire which appeared in the eastern part of the nature reserve two days ago after lightning struck a pine tree has grown in size and now presents a certain danger,” the head of the emergencies ministry for the Mordovia region, Major General Vyacheslav Kormilitsyn, said in a statement.

The fire had grown to an area of 1,000 hectares, the local emergencies ministry said in a statement on its website. The fire is in a nature reserve in the district of the village of Popovka, 17 kilometres southeast of Sarov.

“At the current time, efforts are being made to contain the fire within its existing limits and contain it,” General Kormilitsyn added, saying that 2,600 people and 200 pieces of equipment were being used to extinguish the blazes.

A second fire in the nature reserve – in the district of the village of Pushta, 21 kilometres southwest of Sarov – is smaller at 200 hectares and has been contained, the ministry added. Officials emphasised that no fires had been recorded on the nuclear site itself.

In a phone call with his Russian counterpart Dmitry Medvedev, US President Barack Obama said USAID, the Department of Defence, the Forest Service, and the state of California were mobilising firefighting equipment to help Russia. The first deliveries began yesterday of $2.5 million worth of equipment – including water tanks, pumps, hand tools, fire-protective clothing and medical kits – the State Department said.

After a record heatwave lasting over a month, the first significant rain for weeks poured down on Moscow overnight, with the capital enjoying much lower temperatures of up to 30 degrees Celsius.

There was little sign of the smog from the wildfires that had blighted the Russian capital in the last week but new reports emerged accusing the authorities of hiding the true health toll from the heatwave. Moscow’s top health official has already said the mortality rate had doubled in the heatwave, with hundreds more deaths every day than in usual periods. However the federal authorities have refused to confirm these figures.

The Interfax news agency quoted Moscow doctors as saying they had been forbidden to give “heatstroke” as a cause of death to keep a lid on the statistics.

“We received the order not to use the diagnosis ‘heatstroke’. We are told that the statistics for heatstroke were mounting up,” one doctor told the news agency.

Interfax said the heatwave had also forced Russia to stop producing biometric passports for a week after condensation infiltrated the server at the unit where they are produced when its air conditioning broke down.

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