CHARLESTON — The West Virginia National Guard joined in battling wildfires Friday that have scorched more than 6.25 square miles in the state and destroyed several homes.

Two Blackhawk helicopters dropped water from buckets on the fires in steep, wooded terrain in Hardy County, the National Guard said on social media. The lightweight, flexible buckets hold up to 630 gallons of water.

The fires began earlier this week amid gusty winds and low relative humidity.

In Virginia, more than 100 fires popped up Wednesday, many of them in the central part of the state, forcing the closure of sections of Skyline Drive and the Appalachian Trail. A fire ban was put in place for all of Shenandoah National Park. Fires also were reported this week in neighboring Maryland.

West Virginia Gov. Jim Justice declared a state of emergency Thursday in the northeastern counties of Grant, Hampshire, Hardy and Pendleton, enabling state resources to be allocated and to expedite emergency response efforts.

“Our crews are some of the best in the nation and we will continue to support efforts to combat these fires until our partners with the Division of Forestry say the danger has passed,” National Guard Lt. Col. Todd Justice said in a statement. “We will do all we can to protect our fellow West Virginians and work to keep local responders safe.”

The statement said more equipment and National Guard personnel may be deployed if needed. Volunteer fire departments from across the state also have helped with the fires.

Hardy County, along the Virginia line less than a two hours’ drive from Washington, D.C., has about 14,000 residents, considerable poultry and other agricultural operations. It also offers tourists an array of river float trips and hiking and cycling trails.

Paul Lewis, Hardy County’s emergency management director, said there were three ongoing fires in the county, including one initially believed to be under control that had worsened near Wardensville. As many as four homes were destroyed in the county, along with an undetermined number of outbuildings, camps and hunting grounds.

“We’re not sure of the total number yet because some of those fires are still active in a couple of those areas,” Lewis said. “Most of these are in the mountains. There’s been a lot of smoke in the area today.”

West Virginia regulators issued an air quality advisory Friday in eight counties. The Division of Air Quality said that some sensitive groups could have breathing difficulties because of the fires, including children, elderly people and others suffering from asthma, heart disease or other lung diseases.

“We were hoping with the rain moving in later this evening that that will help us a great deal,” Lewis said.