A brush fire broke out Thursday along northbound Interstate 15, just north of Escondido near the Deer Springs Road exit.
"On this incident, we had all the air tankers, both helicopters and then, of course, approximately 12 fire engines," said Cal Fire spokesman Issac Sanchez.
When Cal Fire units arrived, they discovered a quarter acre fire and immediately requested additional crews for backup, said Sanchez.
Firefighters at the scene are working to extinguish the flames. CHP officers along with San Diego County Sheriff’s deputies were called to the area at 2:30 p.m.
Just before 4 p.m., the fire's forward rate of spread stopped at three acres.
Old Castle Road and Champagne Boulevard will remain closed for several hours, according to Cal Fire.
Smoke was impacting the freeway at one point, but the northbound I-15 currently remains open, said Sanchez.
Investigators are working to determine the cause of the fire.