A state of emergency has been declared in Arizona after the fast-spreading Flagstaff Fire doubled in size this week, threatening hundreds of buildings in the area.

The fire is ravaging large areas around the city of Flagstaff in Coconino County in the US state of Arizona after first being reported on Sunday.

The blaze doubled in size to nearly 20,000 acres during Tuesday night, prompting officials to declare a state of emergency the next day.

As of Wednesday, forest officials said the blaze was still at 0 percent containment.

Fire Management Officer True Brown urged residents to evacuate the area, stating: “I cannot stress enough how rapidly this fire is moving in a north-easterly direction.”

Officials said 25 structures have been severely damaged so far while a further 250 are at risk.

Meanwhile, local reports said flames, being fanned by winds of around 50mph, have reached heights of up to 100 feet.

As of Wednesday, nearly 800 homes had been evacuated in Coconino County in an affected area with over 2,000 residents.

Coconino Sheriff Jim Driscoll said: “The rapid movement of the progression of this fire made the evacuation much more difficult and complicated than we’ve had in the past.

“We had some difficulties getting some people to leave and we’re still trying to confirm those that may have chosen to stay in their neighbourhoods and not honour the mandatory evacuation.”

National Weather Service meteorologist Brian Klimowski said a red flag alert has been issued for today (21st April) due to high winds causing further spread, adding that a strong front is expected on Friday.

Klimowski said: “It’s going to be dry. So, folks, we have entered our fire season. It’s going to be a long one this year.”

Meteorologist Robert Rickey stated: “I don’t see any significant decreases in wind, I don’t see any big bump-ups in humidity and, at this point, we’re not really expecting any precipitation either.”

The cause of the fire is currently under investigation.