The search for former Glee star Naya Rivera continues, 24 hours since the actress was reported missing after disappearing during a boating trip with her four-year-old son.

The Ventura County Sheriff’s office said on Thursday the 33-year-old was presumed to have drowned and the effort to find her was classed as a “search and recovery operation”.

Rivera went missing on Wednesday while on a rented boat with her son Josey Hollis at Lake Piru, about 56 miles north-west of central Los Angeles.

A huge search operation has been launched but she is yet to be found.

Ventura County Sheriff Sergeant Kevin Donoghue provided an update on Thursday and said CCTV from the dock shows Rivera’s boat departing.

He also revealed it may be weeks before any body is found.

Sgt Donoghue said: “If the body is entangled on something beneath the water, it may never come back up.”

He added: “There’s no way to really say. We’re putting our best foot forward to try and locate her, we’re using all the assets that are available to us, we’re using technology like Sonar.”

Sgt Donoghue said experts involved in the search know the lake “inside and out,” adding: “We’re relying on their expertise to help us in that endeavour. We’re going to do everything that we can to find her.”

Rivera’s boat was found drifting in the northern part of the lake, with her sleeping son on board. She was nowhere to be seen.

Josey is safe and with family. Police have since released the 911 call raising the alarm.

The caller, a woman whose husband was one of the first people to find the child, mistakenly identified the four-year-old as a girl.

The lake is closed while the search is carried out, Sgt Donoghue said. Diving teams and air operations will stop at nightfall before resuming in the morning.

Rivera’s family are waiting anxiously nearby for news, police said.

Rescuers are battling perilous conditions. The depth of the lake differs greatly, officer Chris Dyer said, saying it can go from between 50-60ft to 4ft over a short distance.

Visibility in the lake during the daytime is about eight to 10 inches, while sizeable debris including trees flow beneath the surface, police said.

More than 100 rescuers are at the lake and involved in the effort to find Rivera, with “multiple dive teams” searching the murky depths while two helicopters continue to scour the waves from above.

The task has been complicated by rising winds, with the surface becoming choppier.

Rivera rented a boat at about 1pm on Wednesday and spent the afternoon swimming with her son, police said. The child, who was wearing a life jacket, returned to the boat, while his mother did not.

The boy was found asleep on the boat after suspicions were raised when the rented boat was not returned on time.

Police said Rivera’s purse, including ID, were on board, as well as a life jacket.

The rescue mission was called off at around 10pm on Wednesday and resumed at dawn on Thursday.

Rivera found significant success starring as a high school cheerleader in Glee. She looks increasingly likely to become the third major cast member to die in their 30s.

Co-star Mark Salling, who Rivera dated at one point, 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.

Rivera became engaged to rapper Big Sean in October 2013, but they ended their relationship in April 2014.

She then began dating actor Ryan Dorsey and they married in Mexico in July that year.

The couple had son Josey in September 2015.

Rivera filed for divorce after two years of marriage, but they later called off the separation before finalising their divorce in June 2018.

Pop star Demi Lovato and Rivera’s former Glee co-stars were among those sharing their hopes for her safe return on social media.