LOS ANGELES (AP) — Authorities were searching the waters of 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.

The Ventura County Sheriff's Department said helicopters, drones and divers including some from other agencies were joining the search that was suspended overnight after several hours Wednesday. It 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.”

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 lake's popular recreation area, which is technically a reservoir. It was shut down Thursday for the search.

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 “my greatest success, and I will never do any better than him” in her 2016 memoir “Sorry Not Sorry.”

The actress 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.”

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.

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Follow AP Entertainment Writer Andrew Dalton on Twitter: https://twitter.com/andyjamesdalton.