At least two firefighters were shot and killed Sunday by unidentified suspects while responding to a wildfire near Coeur d'Alene in the U.S. state of Idaho, local officials said.

Kootenai County Sheriff Robert Norris told a press briefing that both victims were fire personnel, saying the number of the injured remains unknown, and the firefighting operation is ongoing.

The incident occurred at approximately 1:30 p.m. local time (2030 GMT) on Sunday after a brush fire broke out on Canfield Mountain. As firefighters arrived at the scene about 30 minutes later, they came under gunfire from unknown individuals hiding in the woods, according to law enforcement sources.

The shooter or shooters are using "modern-day sporting rifles," Norris said.

The search for suspects is ongoing. According to Norris, the situation remains active and authorities are currently taking fire from multiple directions on the mountain.

"We still have civilians who are coming off that mountain. We might have civilians that are stuck or in shock on that mountain, so this is a very, very fresh situation," Norris said.

Authorities have not confirmed the number of shooters. Norris noted that if they aren't stopped soon, "this is likely to be a multiday operation."