The ground below the shoulder of the 5 Freeway gave way Wednesday, prompting Caltrans to reduce lanes on both sides of the interstate near Castaic.
The mudslide began several days ago, but continued growing over the weekend and into the week, according to Eric Menjivar, a spokesperson for Caltrans.
On Wednesday, the hillside worsened and damaged a part of the shoulder on the southbound side of the freeway.
Temporary railings, aka K-Rails, were placed on the side of the roadway Monday and engineers from Caltrans responded to the scene to examine the area.
The southbound side of the road is reduced to two lanes around six miles south of Liebre Gulch, according to the California Highway Patrol. The northbound side is reduced to three lanes from about nine north of Santa Clarita due to another mudslide that occurred in January.
Those current lane closures will remain in effect for the foreseeable future, Menjivar said.