The flames appeared to be burning in three different nearby spots, sending thick plumes of smoke into the air over the 210 Freeway in the Irwindale area.
Helicopter were picking up water from the lake to drop on the fire as crews also attacked from the ground.
Dry conditions and strong breezes were helping spread the fire as it continued to grow.
The fire was first reported around 3:30 p.m. and was soon upgraded to a 2nd alarm to help add resources.
Forward progress was stopped by around 5:25 p.m. with containment listed at 60%.
The cause remains under investigation.