A dry brush and vegetation fire in the Cleveland National Forest grew to 170 acres Friday evening, with moderate fire behavior, according to federal forestry officials.

Some evacuation orders are in effect.

The Grade Fire is northwest of Lake Henshaw, far inland in North County, CalFire said, burning on rocky, hilly terrain. East Grade Road at Highway 76 is closed. CalFire reported that the blaze began around 1:30 p.m.

The cause of the fire was not immediately known but is under investigation.

Around 5:45 p.m., Cleveland National Forest spokesperson Daniel Lanari said one structure was under threat, but it was unclear what type of edifice was endangered.

smoke on a shrubby hillThe Grade Fire burns near Lake Henshaw. (Image courtesy Alert California)

Crews are responding from the air and on the ground, according to a USDA Forest Service social media post. CalFire said crews would work through the evening to build a containment line.

“There are currently nine engines, two hand crews, two water tenders, four air tankers, and two helicopters responding to the incident, with a total of over 300 firefighters on scene and more resources being ordered,” federal officials reported.

Ground crews battle the Grade Fire. (Image courtesy CalFire)

Flames are spreading to the east by northeast direction, according to forestry officials, who are fighting the fire in unified command with CalFire. The Forest Service estimated the size of the fire was at 170 acres as of 6 p.m.

Immediate evacuation orders were issued for sections of Fink Road, East Grade Road, and Henshaw Road. Another area is under an evacuation warning.

Officials moved the evacuation point to Harrah’s Casino at 777 Harrah’s Rincon Way.

“If you feel you are in danger, go,” said the San Diego County Sheriff’s Office in a statement.

Smoke spreds across the sky above Palomar Observtory. (Pmage courtesy Alert California)

In addition, the San Diego County Air Pollution Control District issued a smoke advisory for northeastern San Diego, including Santa Ysabel and Warner Springs.

City News Service contributed to this report.