THORNTON, Colo. People forced to flee a rapidly spreading grass fire in Thornton earlier Wednesday were allowed back home hours after the blaze sent a large plume of black smoke into the air that could be seen from miles away.T he fire near W. 84th Avenue and Huron Street started at around 11:30 a.m. and sent smoke drifting over Interstate 25, forcing state transportation officials to fully shut down the highway between Thornton Parkway and W. 84th Avenue for about two hours.As it moved east, the blaze then forced city officials to issue mandatory evacuation orders for residents along a green belt between a neighborhood to the north and businesses to the south, according to Thornton Fire Chief Steve Kelley, who said no Code Red alert was sent to people in the area because the city is transitioning into a new alert system.Instead, he said Pinnacle High School and nearby businesses were immediately evacuated as a precaution as officers went door to door in neighborhoods to the northeast to alert residents of the danger. The fire, aided by strong winds and burning amid red flag conditions, grew to approximately 10 acres in size before it was contained near a fence line on Elati Street close to residential property that the fire never touched, according to Kelley, who provided an update to news media during a news conference later Wednesday."We lost no residential structures as a result of this fire," he said. "We did have damage to some businesses along the south side of the fire" that fire officials are continuing to evaluate, he added. "At this time, it does not appear that there was any damage to the structures."Though the fire is contained, crews will remain at the scene overnight working on hot spots to make the fire does not rekindle. Road closures in the area were also expected to continue through at least Thursday as suppression and containment operations continue, Kelley said.It was not immediately clear how many people were impacted by Wednesday's evacuation orders, but a temporary shelter was established for affected residents at the Margaret Carpenter Recreation Center, located at 11151 Colorado Blvd.During Wednesday's news conference, Kelley said it was his agency's understanding that Pinnacle High would resume classes Thursday.In all, four fighters and one resident were injured as a result of the grass fire. None were considered critical injuries, the fire chief said.Red flag warning conditions persist through late WednesdayMost of the Front Range, including the area where the fire is burning, is under a red flag warning for wind and low relative humidity. The warning expires at 6 p.m. Wednesday.Kelley said his department had not seen a fire like this in the City of Thornton "in at least six months," and said wind conditions contributed to its rapid growth and influenced the scale of the response. But he said a key factor in limiting the fire's spread was not just the fire response, but the city's Parks and Recreations department maintenance of the greenbelt along with residents doing their part to make sure no dry fuels grow in their property.While the cause of the fire remains under investigation, Kelley urged residents to follow burn bans and avoid igniting anything that could create sparks while those bans are in place."The Marshall fire is, I think, on everybody's minds in the metro area, and our intent is not to allow that to happen again," Kelley said, as he talked about the magnitude in response to Wednesday's fire. "Our intent to get ahead of these fires so we don't have the spread of conditions like we experienced during the Marshall Fire. I think we're very fortunate today that we did not have an outcome similar," he added.An estimated 100150 firefighters from 47 different agencies were involved in battling the blaze, Kelley said, including Thornton police and first responders from Westminster, Adams County, Northglenn, Federal Heights, and the Colorado State Patrol. Watch the news conference from the Thornton fire chief in the video player below: News conference: Thornton fire officials provide update on grass fire in Thornton ...read more read less