Fire crews in Contra Costa County are battling a grass fire burning in the area of Pine Hollow Court in Clayton Tuesday morning, according to officials. The fire comes only 12 hours after an overnight wildfire charred more than 8 acres of hillside in Clayton. That fire was reported near Marsh Creek Road at around 11 p.m. The Contra Costa Fire Twitter account posted about the latest incident at around 11:18 a.m. Tuesday. The post said the fire had grown to approximately 4-5 acres with medium spread and was threatening one structure. The fire was reportedly started by an area homeowner who was mowing grass. Local residents were being asked to avoid the area. During the overnight fire, nervous residents of the Clayton Palms Mobile home park watched fire crews battle the flames. Dozens of firefighters were finally able to contain the flames in the predawn hours. Cal Fire said the fire was 75 percent contained by 6 a.m.