OGDEN — A small but smoky grass fire that broke out Sunday near a hiking trail at the mouth of Ogden Canyon appears to be human caused.

According to a press release from the Ogden City Fire Department, a witness reported seeing two juveniles running toward a neighborhood west of the area.

Deputy Chief Mathew Schwenk of the Ogden department said crews aren't sure if the pair started the fire, but investigators are looking for them as they follow up all leads in the case. The fire is being investigated by the Ogden City Police Department and the Ogden fire marshal.

The blaze was reported at about 4 p.m. and had burned about 40 acres as of Sunday evening. The fire's prominent spot on the mountain and highly visible smoke plume generated attention among Ogden residents, but crews reported the grass fire wasn't threatening homes or structures as it moved east.

A 22-person crew using members of the Ogden City Fire Department, Weber Fire District and the U.S. Forest Service was fighting the blaze.

A  helicopter was used to douse the area and contain the flames, keeping the fire from spreading down the canyon.

The helicopter and fire crews worked until nightfall. Firefighting efforts were suspended because of darkness, according to the release, but firefighters were watching the fire overnight and will resume their efforts Monday morning.

Ogden's 12th Street funnels into Ogden Canyon. Crews said the fire seems to have started relatively close to the road. 

McKenzie Romero Twitter: @McKenzieRomero