At least 12 cars involved in massive pileup on WB 91 Freeway in Corona

CORONA, Calif. (KABC) -- At least 12 vehicles were involved in a massive pileup on the westbound 91 Freeway in Corona Thursday morning.

The collision occurred around 4:40 a.m. near Green River Road. Multiple lanes were shut down as emergency crews worked to clear the scene.

Injuries were unknown. Traffic was at a standstill for miles.

All lanes have since reopened, but traffic remained sluggish throughout the morning.