(LOS ANGLES) — Authorities were searching a Southern California lake Thursday for Glee star Naya Rivera a day after her 4-year-old son was found alone on a rented boat.

More than 80 people using helicopters, drones, and all-terrain vehicles, including divers, were involved in the search, the Ventura County Sheriff’s Office said. The search began Wednesday and was suspended overnight, but resumed Thursday morning 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 reservoir’s recreation area, 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.”

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

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.

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 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.

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

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