Investigators believe a small wildfire that was quickly extinguished on Boulder County’s Betasso Preserve open space was human-caused, sheriff’s officials said late Wednesday.

A Boulder County Parks and Open Space ranger saw smoke east of the Bummers Rock Trail on Betasso Preserve at 6:43 p.m. Wednesday, according to a news release from the Boulder County Sheriff’s Office.

Upon closer inspection, the ranger found a small wildfire, about 20 feet by 20 feet, on county property. Firefighters from the Sugarloaf Fire Protection District and Boulder County Sheriff’s Office Fire Management, along with sheriff’s deputies, responded and quickly contained and then extinguished the blaze.

No other property or structures were threatened, officials said.

The cause of the fire remains under investigation by the sheriff’s office, but initial reports indicated it was human-caused, officials said. No one was located or observed in the area when deputies and firefighters arrived.

Anyone with information is asked to call the sheriff’s office at 303-441-4444.

Boulder County Sheriff Joe Pelle this week enacted a Level 1 Fire Restriction for the western part of the county, banning open burning as the fire danger increases due to hot, dry weather.

The ban encompasses essentially the entire county west of Colo. 93, Broadway in Boulder and U.S. 36, along with all of the Rabbit Mountain Open Space area and to the west of its western boundary, according to a news release.

People violating the county’s ban are subject to a $1,000 fine and higher fines are possible for subsequent offenses in addition to civil penalties.