An overturned dump truck hauling a boulder is blocking both sides of State Route 78 just east of Ramona, forcing California Highway Patrol to issue a Sig Alert ahead of a large cleanup effort.
The large boulder rolled out of the truck when it turned over near Rancho Santa Teresa Drive.
Traffic is being diverted to Old Julian Highway as a heavy-duty tow truck or big rig responds to upright the dump truck.
More than one truck may be needed, CHP says.
It's unclear how they plan to get the boulder off the road.
There is no word on injuries or the condition of the dump truck driver.
