The 91 Freeway was closed in Corona Sunday night after a report of an active shooter.
Westbound lanes were open as of 10:40 p.m., and eastbound lanes reopened around 11 p.m.
A large police presence could be seen in the area from NewsChopper4.
It was not clear if anyone was injured by the shooter, and a description of the gunman was not immediately available.
Police were searching for the shooter in a nearby residential area.
This is a developing story. Refresh for updates.