UPDATE: 12: 55 p.m.
According to the California Highway Patrol, the semi truck skidded off the transition road, causing its trailer to overturn. The driver was not hurt.
While the eastbound 91 connector to northbound I-15 is open with sluggish traffic, the southbound transition remains closed, according to CHP.
The closure was expected to last a couple of hours, according to the CHP.
City News Service contributed to this report
The California Highway Patrol has shut down the eastbound Riverside 91 Freeway connector to southbound Interstate 15 in Corona due to a big rig crash.
The accident was reported at 12:07 p.m.
CHP is reporting the big rig has gone over the embankment, with the driver possibly trapped.
A SigAlert was issued at 12:19 p.m., according to CHP.