Firefighters are working to contain a wildfire that has burned three days and spread across more than 2,000 acres of Shenandoah National Park, the National Park Service said.

The fire in the south district of the park, on Rocky Mount, had grown to approximately 2,094 acres as of Monday night, the National Park Service said in an update.

A portion of the Appalachian Trail was closed, from Doyles River Overlook (mile 82) to Powell Gap (mile 70). Skyline Drive was closed from Swift Run Gap (mile 65) to Loft Mountain (mile 79). Multiple trails were closed. For the full list, see the Facebook page for the park.

The cause of the fire reported about 1 p.m. Saturday is under investigation.

More than 100 firefighters were battling the blaze, including personnel from the National Park Service, Virginia Department of Forestry and USDA Forest Service. Additional firefighters and equipment were en route as of Monday night.

Most forest fires in Virginia are caused by human actions and can be prevented, the Virginia Department of Forestry says. The department has these tips on preventing fires:

Do not leave a campfire fire unattended. If a fire does escape, call 911 immediately

Keep a supply of water and a rake or shovel near the fire

Start fires only when the wind is calm

Report any acts of arson immediately and note a description of the suspect and their vehicle

Teach child about how to safely set and put out a campfire

About 30 miles north of the wildfire, the search continues for a Fairfax County firefighter, Nicole Mittendorff, who was reported missing Friday.