Reno, NV -

Health officials in smoky Reno have raised the seriousness of an air quality alert to include the general population as a thick haze worsens from a massive wildfire burning more than 150 miles away at Yosemite National Park.

The Washoe County Health District says the air quality index pushed into the red, unhealthy zone Friday with a peak reading of 171.

School officials canceled all outdoor activities in Carson City, Washoe and Douglas counties.

Officials issued an initial alert Thursday for sensitive populations when the index surpassed 100. The 150 level triggers the red alert indicating even people without respiratory conditions may be affected.

Everyone is urged to reduce prolonged or heavy exertion. Such activities should be avoided altogether by the elderly, young and people with heart or lung disease.