Stewart and Gray Road was closed from Paramount Boulevard to Rives Avenue due to the leak, SoCalGas said.
About 8:30 p.m., the utility company said it would take another eight hours to repair the leak and residents in the area should plan to be evacuated until at least Friday morning, the Downey Patriot reported.
Residents and businesses in the area were advised that they may smell a natural gas odor while SoCalGas crews and first responders worked to stop the leak and make permanent repairs.
A countywide notification regarding the gas leak was sent out at about 12:30 p.m. The city of Downey tweeted about 3 p.m. to explain the notification was released using a new emergency notification system and only intended for residents in the area.