Redmond fire officials are trying to determine the cause of two brush fires in southeast Redmond Tuesday afternoon that eventually combined into one large 50-100 acre blaze. The fires prompted the closure of the airport and COCC Redmond and forced planes to divert to other airports. The low humidity, extremely dry conditions,  and excessively high temperatures have posed an especially tough challenge for firefighters. Businesses in the area were evacuated - some hosing down their roofs beforehand. The fires caused local road closures in Redmond as well as delays on highway 97 and the partial closure of 126 where the fire jumped from one side of the road onto the other.  The wind is still fueling the flames. Fire officials estimate close to 50% containment.