LOS ANGELES — Authorities were searching a Southern California lake Thursday for “Glee” star Naya Rivera who was feared drowned after her 4-year-old son was found alone on a rented boat.

More than 24 hours after she was last seen, over 80 people using helicopters, drones, and all-terrain vehicles, including divers, were involved in the search for Rivera, which began Wednesday afternoon on Lake Piru, 55 miles (90 kilometers) northwest of Los Angeles in the Los Padres National Forest.

Rivera rented a pontoon boat at about 1 p.m. Wednesday, and planned to go swimming with the little boy in the area reserved for recreation, authorities said. Another boater found her son on the north end of the lake asleep on the boat and wearing a life vest.

"We're going on the belief that she did go in the water and we have not been able to locate her," Sheriff's Capt. Eric Buschow said at a news conference. "So this may well be a case of drowning."

Rivera's identification was found on the boat and her vehicle was found in a parking area, authorities said. The boy was safe and healthy and with family members.

There have been occasional drownings through the years in the popular recreation area of the lake, which is about an hour's drive from downtown LA. It was shut down Thursday for the search.

Fire department helicopters hovered over the water on a sunny afternoon in the search's second day, and boats of several sizes could be seen skimming the water, the smaller ones searching up creeks and tributaries.

Rivera's 4-year-old son is from a marriage with actor Ryan Dorsey. The couple finalized their divorce in June 2018 after nearly four years of marriage.

She called the boy, her only child, "my greatest success, and I will never do any better than him" in her 2016 memoir "Sorry Not Sorry."

The most recent tweet on Rivera's account, from Tuesday, read "just the two of us" along with a photo of her and her son.

Rivera was engaged to rapper Big Sean in 2013, but their relationship ended a year later. The pair met on Twitter and collaborated musically, with the rapper appearing on Rivera's debut single "Sorry." She married Dorsey a few months later.

Singer Demi Lovato, who played a Rivera love interest in a guest stint on the show, posted an Instagram story that showed a candle with the text, "Please pray for @nayarivera to be found safe and sound."

Other co-stars were expressing similar sentiments on social media.

"We need all the prayers we can get to bring our Naya back home to us," Heather Morris said on Instagram.

Jackée Harry, who starred in the sitcom "The Royal Family" with Rivera when Rivera was a child, said on Twitter that "I've watched her career blossom ever since. Please God, don't cut this life short."

Rivera played Santana Lopez, a singing cheerleader in the musical-comedy "Glee" that aired on Fox from 2009 until 2015. She appeared in 113 episodes of the series and dated co-star Mark Salling, who killed himself in 2018 at age 35 after pleading guilty to child pornography charges.

Cory Monteith, one of the show's leads, died at 31 in 2013 from a toxic mix of alcohol and heroin.