Ventura police said in a tweet, "A body has been found at Lake Piru this morning. The recovery is in progress. A news conference will take place at 2 pm at the lake."
Authorities would not immediately say if the person found was Rivera, but said the day after she disappeared that they believed she drowned in the lake northwest of Los Angeles.
Rivera had experience boating on the lake in Los Padres National Forest, authorities said. She is believed to have drowned “in what appears to be a tragic accident,” the statement said.
When the boat failed to return, its vendor found the vessel drifting in the northern end of the lake late Wednesday afternoon with the boy asleep on board. He told investigators that he and his mother had been swimming and he got back into the boat but she didn’t, according to a sheriff’s office statement.
The boy was wearing a life vest, and another life jacket was found in the boat along with Rivera’s purse and identification. Josey, the son of Rivera's ex-husband, actor Ryan Dorsey, is "in good health," authorities confirmed earlier in the week.
The couple finalized their divorce in June 2018 after nearly four years of marriage.
Rivera is best known for playing singing cheerleader Santana Lopez for six seasons on the Fox musical-comedy “Glee.”
Lake Piru is two miles long and its deepest point is "about 130 feet," Capt. Eric Buschow said previously. Authorities were also using sniffing dogs to assist in the searches.
The lake was searched by dozens of divers working in waters with little visibility, with help above from helicopters, drones, and all-terrain vehicles.
Ventura County Sheriff's did not immediately respond to Fox News' request for comment.
The Associated Press contributed to this report.