A big rig overturns on the 91 Freeway

 A big rig overturned on the Riverside (91) Freeway near downtown Riverside, snagging traffic and prompting a Sigalert.

The crash occurred just before 3 p.m. on the eastbound side of the freeway near the 60/91/215 interchange, according to the California Highway Patrol.

The crash did not involve any other vehicles and the driver of the Walmart truck, which landed on its side, was not injured, the CHP said.

All lanes except the HOV lane were shut down on the eastbound 91 at the crash site, with traffic backed up to University Avenue.

All lanes were also closed on northbound Interstate 215 north of Columbia Avenue, according to Caltrans.