The Ventura County Sheriff’s Office made the announcement on Monday during a news conference, five days after Rivera went missing at the California lake.
Officials had been searching for Rivera since 8 July, when she went missing after renting a pontoon boat with her four-year-old son.
There is no sign of foul play nor any indication that Rivera died by suicide, Sheriff Bill Ayub said during the news conference.
Rivera, 33, began her acting career at an early age and rose to global fame as cheerleader Santana Lopez in Glee, which ran on Fox from 2009 to 2015.
Rivera’s four-year-old son told investigators that his mother, whose body was found in a Southern California lake Monday, boosted him back on to the deck of their rented boat before he looked back and saw her disappearing under the water, authorities said.
“She must have mustered enough energy to get her son back on the boat, but not enough to save herself,” Ventura County Sheriff Bill Ayub said at a news conference.
The boy, Josey Hollis Dorsey, was found asleep and alone in a life vest on the drifting pontoon boat about three hours after they launched on Lake Piru northwest of Los Angeles, setting off a five-day search that ended with the discovery of the body of the 33-year-old floating near the surface early Monday, authorities said.
The mother and son had gone swimming, which was permitted in that part of the lake, Ayub said. She was not wearing a life vest.
Authorities believe that Rivera drowned accidentally, and that her body was most likely trapped in the vegetation under the lake for several days before floating to the top, Ayub said.
Divers had already thoroughly searched the area where she was eventually found, but shrubbery that had grown wildly in the area, which was recently dry, must have kept her hidden in the murky water.
Family members chatted with Rivera via FaceTime when she was on the boat, and search crews watched those videos for clues to where she might have gone down, Ayub said.
“It has been an extremely difficult time for her family throughout this ordeal,” Ayub said “We share in their grief.”
RIvera is the third major cast member from the show to die in their 30s.
Additional reporting by agencies. Read The Independent’s live coverage below:
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Hello and welcome to The Independent's live coverage of the latest developments at Lake Piru, where actor Naya Rivera went missing last week.
The Ventura County Sheriff's Office will hold a press conference at 2pm PT/5pm ET/10pm BST. Officials announced earlier today that a body has been found at Lake Piru.
The news comes after a five-day recovery effort following Rivera's disappearance. The Glee star was reported missing on 8 July after renting a pontoon boat with her four-year-old son.
You can read more about Monday's developments so far here:
Rivera's four-year-old son was found asleep on the boat and wearing a life jacket, according to authorities. The actor's purse and identification was recovered on the vessel.
Some of Glee's former stars have urged fans to stop "judging" those who haven't spoken out on social media regarding Rivera's disappearance:
Officials held a press conference on Monday afternoon confirming they discovered a body in Lake Piru on day six of their search for Glee actress Naya Rivera.
Investigators spoke with her four-year-old son who was on the boat, according to police, who said Rivera helped him back on the boat before he turned around and she had "disappeared".
The body discovered was not wearing a life jacket. Law enforcement do not believe any foul play was involved.
Police said the Glee actress “mustered enough energy” to help get her four-year-old son back on the boat, but added that Rivera was not able to get back on herself.
Investigators will now perform an autopsy and various other reports to further confirm the identity and cause of death.
Naya Rivera fans react to reports actress saved her son in final moments
The Glee actress' fans and supporters are posting heartfelt, emotional responses to today's news conference, in which police said Rivera "mustered enough energy to get her son back on boat but not enough energy to save herself."
More details from the Ventura County Sheriff's Office press conference
Clemence Michallon reports: Naya Rivera’s body has been found, authorities have said.
Officials at the Ventura County Sheriff’s Office announced on Monday they are confident that a body recovered earlier in the day at the lake is that of the 33-year-old actor.
Police have said there is no indication of foul play or that Rivera died by suicide. A post-mortem examination will follow.
Rivera went missing on 8 July after renting a pontoon boat at Lake Piru, about 50 miles northwest of Los Angeles, with her four-year-old son.
An extensive search and recovery effort ensued to locate the missing actor.
Rivera’s four-year-old son previously told police that he and his mother went swimming but she didn’t get back into the boat.
The boy was found asleep on the boat while wearing a life jacket.
An adult-sized life jacket was also found onboard along with some of Rivera‘s belongings.
Rivera began her acting career at a young age before rising to international fame thanks to her portrayal of cheerleader Santana Lopez on Glee, which aired on Fox between 2009 and 2015.
Additional reporting by agencies