CHERRY VALLEY (CNS) — Contending with elevated winds and inhospitable terrain, hundreds of firefighters Thursday continued a slow advance around the 28,000-acre Apple Fire in the San Bernardino National Forest, where a crewman suffered a head injury on the fire lines.

The blaze, which is now 30% contained, is extending on a northeast track at roughly mile-high elevations in the area of Millard Canyon, according to the U.S. Forest Service. An estimated 28,085 acres have burned.

Shortly before noon, a member of one of the hand crews working to dig containment lines was under a tree when a branch toppled onto his head, according to reports from the scene.

The firefighter was aided by medics at the location but required further attention and was taken to a staging area, where he was reportedly picked up by an ambulance. No other details were immediately available, including his identity or condition.

Another firefighter suffered unspecified minor injuries earlier this week.

Winds were expected to blow 10 to 20 mph throughout the day in the fire area, which is within the San Gorgonio Pass, where gusty conditions are not uncommon because of the landscape.

According to the National Weather Service winds were expected to abate Friday.

Officials believe the blaze may be fully contained as soon as Aug. 17. An estimated 2,600 residences and 7,800 people were evacuated at the height of the fire, which erupted in Cherry Valley about 5 p.m. Friday near Apple Tree Lane and Oak Glen Road. All evacuation orders in Riverside County have since been lifted.

The wildfire was sparked by burning exhaust from a diesel-fueled vehicle, according to Cal Fire.

Four homes have been destroyed by the flames, along with eight outbuildings. One of the homes and two of the sheds were located near Avenida Miravilla in Cherry Valley.

The head of the fire is on a mountainside in San Bernardino County, where the vast majority of the 2,500 firefighters who have been deployed are working. A total of 21 aircraft -- 19 water-dropping helicopters and two air tankers -- have been rotating in and out of the fire zone, helping lay down tentative containment boundaries.

The fire has been spreading deeper into San Bernardino County, and the San Gorgonio wilderness, but in the last day, it has expanded less than 800 acres. The wilderness remains closed to all use, including a stretch of the Pacific Crest National Scenic Trail that cuts through it, the USFS said.

In San Bernardino County, mandatory evacuation orders remained in place east of Oak Glen Road, and non-mandatory evacuation warnings in San Bernardino County remained in effect in Forest Falls, Morongo Valley, Rimrock and Pioneertown, according to the Forest Service.

Fire personnel will host a community meeting at 6pm Thursday at the Pioneertown Post Office, 53441 Mane St., where updated information will be provided and residents are invited to ask questions.

Gov. Gavin Newsom announced the state will receive a grant from the Federal Emergency Management Agency to help ensure resources will be available to fight the fire. It will also allow local, state and tribal agencies responding to the fire to apply for 75% reimbursement of their eligible costs.

Along with county fire crews, personnel from the Calimesa, Morongo, Murrieta, Palm Springs, Cathedral City, Huntington Beach, Hemet, Pechanga, San Bernardino, Soboba, Los Angeles, and Los Angeles County fire departments were sent to assist under a mutual aid request.

Residents or others with questions and concerns about the fire can call 909-383-5688.