Humanity’s burning of fossil fuels directly led to the deaths of at least 1,500 people in a European heatwave last week, a landmark study said.

A blaze in southern France forced the closure of the Marseille airport, and weather agencies issued warnings for other parts of Europe where temperatures were expected to climb this week.

Researchers said they believe that human-driven climate change probably intensified the recent European heat wave and increased the number of heat-related deaths.