A 155-acre brush blaze burning in Trabuco Canyon that injured four firefighters is 5 percent contained, fire officials reported Wednesday evening.

The fire started around 5 a.m. off Trabuco Creek Road, in the Bell Ridge area of the Cleveland National Forest, the Orange County Fire Authority reported. The fire was burning in an area of tough terrain near Holy Jim Canyon, which is east of Rancho Santa Margarita, officials said.

The fire is being slope driven and spreading based on the angle of the hill, and not by the wind-driven, said Captain Larry Kurtz of the OCFA. No structures were being threatened.

Four firefighters were injured battling the blaze, the Orange County Register reported.

At least 150 firefighters were on the ground battling the fire, while seven air tankers  and 11 helicopters were attacking it from the air.

Holy Jim Canyon was closed due to the fire.

Smoke could be seen across Orange, Riverside and San Bernardino counties.

The cause of the fire was under investigation.

KTLA’s Cindy Von Quednow contributed to this story.