Authorities in Southern California previously said Rivera, 33, was presumed dead after a boat outing Wednesday with her 4-year-old son. The child was found alone Wednesday in the boat they had rented at Lake Piru, north of Los Angeles.
A search for Rivera ended late Thursday with plans to resume Friday, KNBC-TV of Los Angeles reported. The search was already declared a recovery operation by the Ventura County Sheriff's Office.
Rivera and her son had rented the pontoon boat around 1 p.m. and another boater discovered her son sleeping in the craft three hours later. Crews were also out searching for the boat at the time as her rental had expired.
"The emergency is we have a missing person,” a caller reported to 911 around 4:40 p.m., the Ventura County Sheriff’s Office said, according to FOX 11 in Los Angeles. “We found a little girl in one of the boats by the south end (of Lake Piru) but her mom's nowhere to be found."
She said she hadn’t seen the child who her husband found sleeping in the boat. The child turned out to be Rivera’s son, Josey, who has long hair.
The boat was found in an area of the lake around 30 feet deep with 15 feet of visibility, officials said. Along with Josey, who was wearing a life jacket, officials found Rivera’s purse and an adult life jacket in the boat. Her car was found in the parking lot, according to FOX 11.
Josey told investigators Wednesday that he and his mother had gone swimming during their excursion but she never got back into the boat. He had been wearing a life jacket but she wasn’t, he said.
Investigators closed the lake Wednesday as they searched into the night for the actress.
The Ventura County Sheriff's Office said Thursday that "difficult conditions" such as low visibility in the lake made the search "a very slow process."
Officials said Rivera had been to the lake before but it has strong rip currents and it's easy for even experienced swimmers to get tangled in debris, KCAL-TV reported.
Surveillance video of the dock showed Rivera and her son were the only two people to get into the boat and investigators said foul play wasn’t suspected.
"We have no indication, after talking to her son, that Miss Rivera made it to shore,” Sheriff’s Sgt. Kevin Donoghue told reporters, according to FOX 11. “So the focus of our search efforts are in the water. He gave enough information to investigators to conclude that his mother never made it out of the water."
Rivera is best known for playing Santana Lopez on "Glee" and most recently has played Collette Jones in the series "Step Up: High Water."
She was married to actor Ryan Dorsey, Josey's father, from 2014-2018. He has now been reunited with Josey, according to People magazine.
Fox News' Nate Day contributed to this report.