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Huge fires in and around California's Yosemite National Park have continued to spread and now cover an area the size of Edinburgh.

The fires have been burning uncontrollably for more than a week.

Drought conditions and high temperatures helped the flames spread quickly through the trees and the bush.

More than 3,000 firefighters are still trying to control it, creating defence lines with controlled burning to stop more devastation.

Controlled burning is where firefighters burn an area of land on purpose, so that when the wild, larger fire reaches it there's nothing left to burn, so it stops the fire in its tracks.

Knock-on threat to San Francisco

Ash is now falling from the sky onto a nearby reservoir that supplies water and hydro-electric power to the city of San Francisco 150 miles away.

Officials say they're moving water to lower reservoirs and checking on supplies for pollution.

The blaze is also threatening thousands of homes and some of the oldest trees on Earth.

California Governor Jerry Brown declared a state of emergency for San Francisco as the fire could damage power lines that bring electricity to the city.