Searing temperatures fuelled wildfires and prompted health warnings across Europe on Wednesday, as a blaze in Turkey forced the closure of the Dardanelles shipping lane and winds fanned the flames in Greece where 20 people have already been killed.

France, which widened its heatwave red alert in the south of the country, said it would scale back production at a nuclear power plant as high temperatures curbed cooling water supply.

In Greece, firefighters battled a blaze for a second day close to Athens, and authorities warned that heat and winds risked stoking more wildfires a day after 18 bodies, probably migrants, were found in a charred northern forest.

A wildfire north of Athens that erupted on Tuesday has smothered the capital in smoke and ash, spreading to the town of Menidi, where about 150 people were evacuated from three nursing homes. Police ordered others to leave as a helicopter clattered overhead to drop water onto the conflagration.

“The fire went out for half an hour…. but with these very strong winds, it’s been alternately starting and then stopping again,” 60-year-old resident Dimitris Armenis told Reuters.

A volunteer carried an icon of the Virgin Mary out of a burning monastery, while police raced to remove large gas canisters from the ash-covered premises.

Another 700 people were moved from a migrant camp in the Amygdaleza region, about 25 km (16 miles) north of Athens, a Migration Ministry official said.