Undiscovered Second World War bombs and tank shells have been exploding as fires have spread across a large area of the North York Moors.
Fire crews have been battling the vast blaze at Langdale Moor – now said to cover 2,000 acres – for more than two weeks.
The Moorland Association said at least 18 blasts had been triggered as peat burnt down to hidden ordnance, “forcing firefighters into a very defensive firefighting strategy”.
North Yorkshire Fire and Rescue Service warned people living nearby that they might want to prepare a “grab bag” in case they have to leave their homes at short notice because of the risk of the fire spreading and the smoke.
The blaze, which has closed roads and a campsite, and diverted coast-to-coast walkers, is on an area that included a tank training ground in the 1940s.
County chief fire officer Jonathan Dyson said it was a significant wildfire and that he had requested help from other services across England.
“As the peat continues to burn down it is finding the World War Two ordnance and therefore exploding and we have now experienced over 18 ordnance explosions within key areas,” he told the BBC.
Crews had made significant progress in containing the fire before the weekend, he said, but the fire had more than doubled in 24 hours because the wind changed and temperatures rose.
“The fire has made a rapid spread further north and across to the northwest,” he said.
Some 10 appliances and 60 firefighters were involved.
The North York Moors Moorland Association, a collection of upland estates, said the massive amount of smoke in the air was causing problems.
On Facebook, the organisation wrote: “Rain is appearing but this will not be a quick fix, it will help dampen down the top fuel load, but it is the burning peat underground that will take some halting.”
It said fire crews, staff, volunteers and farmers were working in extreme conditions “to say the least”.
“It is not just the extreme heat and smoke conditions but the increased risk of exploding WW2 bombs that are causing additional problems and so the necessity of other methods is having to be implemented.”
It’s understood British tanks used part of the moor as a range in the war. Some online commenters said wartime planes dropped ammunition over the area to lighten their loads on returning from missions.
Drivers have again been urged not to ignore road closed signs.
