CASTAIC — A big rig fire partially closed the Northbound 5 freeway in Castaic on Saturday.

By Saturday night the two right lanes were blocked for clean up from the fire, according to Sigalert.

The number four lane remained closed for an unknown duration due to a big rig that had been on fire, the California Highway Patrol reports.

Earlier in the day, the number one, two and three lanes of the northbound Golden State (5), south of CHP Road, in Castaic, were reopened open.

The Sigalert was issued at 9:36 a.m.

No injuries have been reported.

This is a developing story.