Firefighters responded at 2:30 p.m. to the area near Mulholland Drive, where the fire was burning uphill, according to the Los Angeles Fire Department.
The fire department reported light winds in the area as crews worked to establish hose lines around the flames. In an afternoon update, officials said the fire had burned just over three acre.
"Approximately 60 firefighters working on scene at the height of the incident stopped forward progress within 35 minutes," the fire department said.
No structures were damaged. Meanwhile, all southbound lanes of the 405 were closed, impacting the afternoon traffic rush. Some reopened around 4 p.m. and the California Highway Patrol announced just before 7 p.m. that all lanes were reopened.
The cause of the fire remains under investigation.