The fire erupted in the 500 block of Rustic Hills Drive in the Wood Ranch neighborhood. More than 150 firefighters worked to contain a blaze, dubbed the Rustic Fire, which had grown to 189 acres.
Ventura County Fire Department officials requested additional firefighters from Los Angeles and Los Angeles City fire departments, as well as a fixed wing aircraft.
PHOTOS: Fire burns through hillside in Simi Valley
Firefighters worked tirelessly for hours to contain the flames. One firefighter was hospitalized after suffering from dehydration.
No evacuations were ordered, but residents in areas south of Long Canyon Road were asked to shelter in place.
Residents captured photos of the smoke billowing dangerously close to homes. Others reported seeing smoke from as far as Malibu.
The cause of the fire is under investigation. As of 8:30 p.m., the blaze was 50 percent contained.
This was the second fire to break out in Simi Valley. Earlier Friday morning, a crash on the 118 Freeway near Rocky Peak Road sparked a fire after a truck plunged 200 feet down an embankment.
The blaze scorched about 15 acres. Crews from Los Angeles County, Los Angeles City and Ventura County fire departments worked to put out the fire.