“We’re presuming that an accident happened and we’re presuming she drowned in the lake,” Ventura County Sheriff Deputy Chris Dyer said at a news conference Thursday.
Search and rescue efforts for the actress have now shifted to a recovery operation, Dyer said.
“The goal is still to bring Miss Rivera home to her family,” he said.
Rivera, 33, vanished from Lake Piru on Wednesday evening. She went to the lake that afternoon and rented a pontoon boat with her 4-year-old son, according to authorities.
Dyer said Thursday that the boat was overdue for return around 4 p.m. local time. A rental employee found the boat on the north end of Lake Piru.
Rivera’s son was on the boat, but she was nowhere to be found, Dyer said. Search efforts began immediately and continued until about 10 p.m. Wednesday.
Another spokesman for the Ventura County Sheriff’s Office, Capt. Eric Bushow, previously said that the child and his mother went swimming and that she did not get back on the boat. He said the child had on a life vest and an adult life vest was found on the boat.
The child is healthy and with family, Dyer said Thursday morning. CNN has reached out to Rivera’s representatives for more details.
Officials resumed the search Thursday morning, and the lake has been closed during the operation, which involves more than 80 people, the sheriff’s office said on Twitter.
Rivera played Santana Lopez on the Fox show for six years from 2009, and appeared in nearly every episode of the musical-comedy-drama. She was also on the CBS sitcom “The Royal Family” and in the comedy film “The Master of Disguise.”
Fellow celebs, including her “Glee” co-star Harry Shum Jr., shared their concern on social media.
Actress Jackée Harry tweeted a scene she shared with Rivera on the sitcom “The Royal Family” which was Rivera’s first acting job at the age of 4.
“Prayers up for the lovely Naya Rivera,” Harry tweeted. “We starred alongside one another in her first very television series, The Royal Family, and I’ve watched her career blossom ever since. Please God, don’t cut this life short.”
Zack Teperman, who described himself as Rivera’s former publicist, said he was shocked by the news of her disappearance.
“I still can’t believe what I’m hearing and hoping it isn’t true,” he posted on social media. “I’m just sad. Naya Rivera was one of the first people I had the honor of working with back in 2009 when I got into public relations and moved to Hollywood. One of the first people to allow me to give her advice and guide her through those crazy Glee days.”