DENVER Crews are fighting a grass fire on National Forest land five miles southeast of the community of Jefferson in Park County.The 10-acre 821 Fire, as its being called, was first reported around 12:47 Saturday afternoon.No evacuations are in place, and no structures are threatened.According to the U.S. Forest Service, firefighters from multiple agencies and a helicopter are battling the blaze.There is no word on how the fire started.