A fire that started burning in northwestern Colorado three weeks ago has since swelled to 800 acres and is displaying “extreme” behavior, according to federal firefighting officials.

What’s been dubbed the Big Red Fire was caused by lightning in the area of Big Red Park in Routt County around five miles from the Wyoming border on Aug. 19. It has since grown to 800 acres as of Monday morning.

According to Inciweb, the blaze is fueled by mixed conifer – which includes spruce, fir, pine and both live and bug-killed timber.

Firefighters are holding a community meeting to discuss the blaze at 6 p.m. Monday at the North Routt Fire Protection District fire station No. 2.