Rivera, 33, went missing on Wednesday. She had reportedly rented a pontoon boat with her young son.
The Ventura County Sheriff’s Department announced on Wednesday they were searching for a possible drowning victim at Lake Piru, located approximately 55 miles northwest of Los Angeles.
Authorities later confirmed that Rivera is the missing person. A boat and helicopter search began but was suspended at nighttime. Officials said it would resume on Thursday “at first light”.
On Thursday morning, a new update informed the public that Lake Piru would be closed to the public while the search continues.
Dive teams from other agencies in the region are assisting with the search.
Helicopters and drones will also join the search, as they did on Wednesday, and authorities are checking the lake’s 12-mile shoreline.
Officials told NBC Los Angeles that Rivera’s four-year-old son was found alone and asleep on a boat on the lake this Wednesday, three hours after the boat was rented.
“We’re going on the belief that she did go in the water and we have not been able to locate her. So this may well be a case of drowning,” Captain Eric Buschow said at a news conference.
Rivera played cheerleader Santana in the Fox TV series Glee that aired on Fox from 2009 to 2015.
Additional reporting by agencies