UPDATE: Kern County Fire is reporting that the Fort Fire is 85% contained and at 554 acres. Full containment is expected by 8 p.m. tonight.

ORIGINAL STORY: A brush fire is burning on the Grapevine near Interstate 5, slowing traffic and threatening power lines.

The Fort Fire broke out at around 11:15 a.m. near the northbound lanes at the east escape ramp, the Kern County Fire Department said Friday.

The fire currently has 0% containment and has burned 300 acres, according to Cal Fire. No homes are threatened, but the flames were threatening radio towers and nearby power lines

Images of the fire could be seen on Caltrans cameras in the area, and KCFD crews reported that traffic was slowing along the freeway.

It wasn't immediately known what caused the fire.