BRUSSELS, Belgium: European countries reported more than 10,000 extra deaths during the record-breaking heatwave that hit western parts of the continent in late June, according to official data.

Most of these deaths, more than 9,000, were among people aged 65 and older. This information came from data published by EuroMOMO, a network supported by the European Center for Disease Prevention and Control and the World Health Organization.

Extreme heat can be deadly. It can cause heat stroke or make heart and breathing problems worse. Older people are among the most at risk.

Lasse Vestergaard, Chief Physician at Denmark's Statens Serum Institut, which hosts EuroMOMO, said that having such a high number of extra deaths at this time of year was unusual and very high. He added that it was difficult to explain the high number of deaths by anything other than the extreme heat.

Scientists said the late-June heatwave would have been almost impossible without human-caused climate change, which is making heatwaves more frequent and more intense.

The data came from national death records in 27 European countries. It included all extra deaths, not just those directly caused by heat, during the week from June 22 to 28, when the heatwave was at its worst in France, Spain, Britain and other countries.

Scientists said there were no other major known factors, such as COVID-19 outbreaks, that could explain the rise to 10,650 extra deaths during that week.

In contrast, over the previous eight weeks, the same countries had about 500 fewer deaths per week than usual. EuroMOMO noted that the data may be updated in the coming weeks as more information becomes available.

The extreme heatwave at the end of June also caused power cuts, school closures, and record-breaking temperatures in France, Spain and the UK.

EuroMOMO does not provide extra death figures for each country, but it said that France and Belgium were the only countries in Europe to record "very high" excess deaths in the last week of June.

Belgium recorded its highest excess death rate during any heatwave since records began in 2000, according to its public health institute, Sciensano.

A separate scientific study published on July 13 estimated that 2,700 people died from heat-related causes in England and Wales alone during the May and June heatwaves.

The study found that 42 percent of those deaths were due to the additional heat from global warming. Imperial College London, the UK Met Office, and the London School of Hygiene and Tropical Medicine conducted this research.

Meanwhile, more than 400 French firefighters worked through the night to control a wildfire in the historic Fontainebleau forest, south of Paris. On July 13, authorities also sent two water-bombing planes to help fight the fire as a heatwave continued across western Europe.

The fire started near a highway close to Fontainebleau, which is home to one of France's most famous royal palaces. The palace was once used as a hunting lodge and an autumn home by former kings. By midnight, the fire had burned more than 800 hectares (1,980 acres), helped by strong, hot winds.

The forest is about 70 kilometers (43.5 miles) from Paris. The fire forced the closure of the A6 highway, which connects Paris to Lyon and southern France. Smaller fires in the area also disrupted high-speed train services.

The French fire service said that the firefighting efforts were continuing. Residents were warned that the Canadair planes would need to collect water from the River Seine, which flows through central Paris.