Fire crews have a grass fire burning south of Butte close to 50 percent contained.

The fire broke out Tuesday around 4 p.m. near Buxton and quickly spread.

Officials revised earlier estimates and put the blaze at around 30 acres.

It threatened some homes, but crews were able to protect them. No one was evacuated.

"Were in red flag conditions today for low humidity and higher winds and as a result of that this fire did spread rapidly as you can see it obviously moves faster in grass which is pretty normal but we got a good response from the county as well as forest service folks to get on this and were able to hold this on the East flank," Joe Sampson with the U.S. Forest Service said.

At least three crews and two helicopters are on the fire. Firefighters expect to be on the scene until after dark.

Sampson said they used helicopters from the Pony Fire.