SAN DIEGO — A Sig Alert has been issued for an overturned semi-truck on the southbound lanes of Interstate 805 in Chula Vista.

Lanes one through three near Bonita Road are currently closed, as crews work to recover the truck. California Highway Patrol has officers on the scene and are directing traffic through the open lane.

CalTrans said that the current estimated time for lane reopening is unknown.

It is unknown what caused the semi-truck to turn on its side.

CalTrans said that the truck was jackknifed. It is unknown if other vehicles were involved in the accident.

This is a developing story. Check back for updates.