A wildfire has forced the evacuation and closure of a small campground in northeast Yellowstone National Park, the first visitor facility in the park to be affected by wildfires this summer.

In addition, firefighters are trying to keep another fire from burning outside the park's western boundary where it would threaten several private subdivisions in Montana.

All other major Yellowstone tourist facilities and attractions, including Old Faithful, and all park entrances are open. However, the park on Thursday banned all charcoal and wood fires at all campgrounds, campsites and picnic areas because of the warm, dry and windy weather conditions.

Fire spokesman Bill Swartley said Thursday the fire that closed the Slough Creek Campground burned actively overnight and firefighters were working past midnight to suppress spot fires being started ahead of the main fire.

The Slough Creek Campground is the smallest of the developed campgrounds in Yellowstone with 23 sites.

Swartley said he didn't know how many campers were using the campground when it was evacuated earlier this week. Other backcountry campgrounds and trails in the area also have been closed.

Swartley said the fire that closed the campground was unusually active through Wednesday night.

"Critical fire weather conditions are in play, but it's just how the fires respond to them and one of the fires was quite active," he said.

The fire is one of five burning in Yellowstone. The largest fire has burned nearly 60 square miles north of the West Entrance Road, and firefighters are working to keep it from spreading beyond the park's western boundary.

Firefighters were expecting warm, dry and windy conditions to be conducive to fire growth into Saturday.

In neighboring Grand Teton National Park, a wildfire that had closed a road leading to Yellowstone's south entrance last week was still growing, but it was mostly burning in remote areas and no longer affects travelers between the two parks.