PECOS, N.M. (AP) - Firefighters battling a blaze that has charred thousands of acres in northern New Mexico scrambled to protect water sources as they learned the fire is more than three times larger than originally feared. Flames surged through dry timber Wednesday in the Sangre de Cristo Mountains, threatening the Pecos Wilderness and the main watershed for Las Vegas, N.M. There have been an undetermined number of evacuations but no serious injuries reported. Aided by infrared mapping, officials found Wednesday that the fire had ballooned from 6,500 acres Tuesday to 23,500 acres Wednesday and was at the upper edge of the Gallinas Canyon, which supplies Las Vegas with water. "The far north end of the fire has reached what is essentially considered the upper portion of the Gallinas watershed," said fire information officer Maria Garcia. "However, water quality has not been affected." The blaze was 15 percent contained late Wednesday. It is in the forests east of Santa Fe and some 70 miles from Los Alamos, where the worst fire in state history last month burned more than 45,000acres and destroyed more than 200 homes. Gov. Gary Johnson flew over the Gallinas and Santa Fe watersheds Wednesday afternoon. He warned there could be "a true catastrophe" if trees are not thinned and brush isn't cleared. "I think this flight really points out the importance of preventive maintenance for all the watersheds in New Mexico, "Johnson said. After searing heat, lower temperatures and higher humidity have aided firefighters. The forecast today called for partly cloudy skies with a slight chance of afternoon thunderstorms. The massive columns of smoke that roiled skyward Monday and Tuesday were gone Wednesday as smoke lay flat over the area. Theair was hazy and smelled of smoke in Las Vegas, about 12 miles awayand out of the path of the fire. Air tankers have been dropping fire retardant on the flames and helicopters have been dumping huge buckets of water since the fire broke out Monday. More than 1,000 firefighters and support staff were on the scene. The area is checkered with small ranches, clumps of dwellings and several camps.