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COLORADO SPRINGS, COLO. -- El Paso County Public Health officials said the haze seen in Colorado Springs Thursday is from the High Park Fire burning near Fort Collins.

Officials also said the air quality in the city Thursday will be worse than Denver. Denver is about 60 miles closer to the fire burning in Larimer County, but because of winds blowing south, the haze has shifted into southern Colorado.

Colorado Springs Fire officials said they have received several calls already Thursday for smoke investigation.

Public Health officials in the county have issued an air quality alert and said the air could be unhealthy in your neighborhood if visibility is fewer than five miles.

The air quality index is listed as "unhealthy" for Fort Collins and "moderate" for Colorado Springs but "good" for Denver.

Officials said it is best to stay indoors, but if you have to be outside, avoid stressful outdoor activities. They also said it is best to keep windows closed.

The fire, which started because of a lightning strike over the weekend, grew rapidly and is the largest wildfire the area has ever had. It is currently 10 percent contained and ahs grown to about 78 square miles, though officials said Thursday growth is the slowest seen since it began.

Hundreds of people remain evacuated, and one person has died so far. More than 100 structures have been destroyed.

More than 1,200 firefighters have been working around the clock. They're working to protect homes and are also trying to keep the blaze from spreading past a highway that runs along a canyon cut by the Cache La Poudre River.

Information from the Associated Press was used in this story.