The North Hills Fire grew to around 4,200 acres Monday morning as crews continue to battle the wildfire north of Helena.
According to Lewis and Clark County Emergency Management, the latest estimate is the result of an infrared flight conducted Sunday evening. Officials said, so far, no structures have been lost.
A larger Type Two incident management team is scheduled to take over management of the fire Monday as it threatens property and has forced hundreds of evacuations.
At a briefing on Sunday, authorities say winds pushed the fire toward homes, but firefighters fought aggressively to protect neighborhoods.
More updates are expected at a public meeting scheduled for Monday evening at 6 p.m. at the Helena Valley Community Center at 3552 Tizer Road.
The Red Cross opened an evacuation shelter Sunday evening. The shelter is at Helena First Assembly of God Church, at 2210 Dodge Avenue.