Tens of thousands of people have been told to evacuate from an area close to Reno, Nevada, as a large wildfire reached the outskirts of the city.

Around 42,000 people have been ordered to leave their homes immediately, with a further 45,000 people urged to get ready to leave.

Officials warned the fire was expected to burn for two more days and said there was no timeline for people to return to their homes.

The fire, which was first reported on Saturday morning, had so far injured six people, officials said. Windy and unpredictable weather conditions have contributed to its spread.

Nevada’s Governor Joe Lombardo has declared a state of emergency in Washoe County and ordered the National Guard to join firefighting and law enforcement efforts.

“This is an active and rapidly evolving situation and I urge everyone in the affected areas to remain vigilant and follow the direction of local officials,” he said.

The fire was caused by humans and first reported at 11:15 local time (18:15 GMT) on Saturday, according to local officials.

The Washoe emergency information centre said around 15,000 acres (23 sq miles) had been burned.

Chief Richard Edwards of the Truckee Meadows Fire Protection District – which covers the county said on Monday that the fire “continues to grow” and no part of the fire’s perimeter had yet been contained, CNN reported.

Around 13,700 homes were inside the evacuation area, local emergency services said, with two shelters set up to take in displaced residents.

Of the six injured, three were emergency responders fighting the fire.

Over the weekend, local officials described the fire as fast-moving, with windy weather and dry conditions contributing to its spread.

“The fire has definitely exploded in size,” Lucia Starbuck, a local reporter for KUNR Public Radio, told the BBC.

“It’s burning these dry desert hills with neighbourhoods at the bottom. We know some homes have been burned, we don’t know the exact number yet.”

All Washoe County schools will be closed on Monday, except one, and mass road closures are in place.

The immediate “go now” evacuation zone and wider “get set” area – where people are being warned to prepare to evacuate – do not extend to the centre of Reno, but do affect large urban areas and part of a highway.

The University of Nevada in Reno – which has its main campus in the city, outside of but close to the “get set” warning area – said regular campus operations would continue but that it was monitoring the situation.

Large air tankers and helicopters have been flying over the affected area dropping water and fire retardants.

Justin Davis, 29, lives on Peavine Mountain, close to Reno, and watched as the fire spread towards his home on Saturday and destroyed four of his vehicles.

He told the BBC he had previously bought a water truck in case a wildfire like this occurred and had used it to save his home.

“We turned on the water truck and just started spraying down the things we wanted to save,” he said.

The blaze has been been named the Hawk Fire because it was first reported near the Hawk Meadow Trail, to the west of Reno.

Reno, in western Nevada, is located close to the state boundary with California and has a population of around 280,000 people.

Wildfires are common in south-western US states, including Nevada, and are becoming more severe, according to the National Oceanic and Atmospheric Administration. There are currently three large fires in the state, out of a total of 79 nationwide.

However, many of these fires develop in rural and less populated areas, with only a few encroaching on population centres.

Scientists say that human-induced climate change makes the warm, dry conditions that facilitate the rapid spread of wildfires more likely.

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