The ramp from southbound state Route 15 to northbound Interstate 5 was closed for nearly one hour as crews battled three small brush fires in the area.
The fires erupted at about 2:25 p.m., San Diego Fire spokesman Lee Swanson said, but were knocked down in less than 30 minutes. Arson investigators were trying to determine the fire's cause.
SDFD crews and one National City Fire Department engine were sent to the scene to battle the three small fires. California Highway Patrol reopened the ramp before 3:40 p.m.
No injuries were immediately reported.
KPBS media partner 10News contributed to this report.
