Rivera, 33, disappeared from Lake Piru in Ventura County on Wednesday evening. The Ventura County Sheriff's Office said the search would resume "at the first light" and called it a possible drowning.
Rivera went to the lake on Wednesday afternoon and hired a boat with her young child. The two were seen dating on the lake, said Sheriff Eric Buschow's captain at a press conference.
About three hours after leaving the dock, another boater discovered a boat drifting with the sleeping child on board. Authorities were informed and began searching from the air and with a diving team.
Although it was difficult to obtain information, the child said that they had gone swimming but that the mother had not returned to the boat, said Buschow. He said that the child was wearing a life jacket and that an adult life jacket was found on the boat.
Rivera has a 4-year-old son and local media reports that he was found on the boat. CNN contacted its representatives for more details.
She played Santana Lopez on the Fox show for six years from 2009 and appeared in almost all episodes of the musical-comic drama. She was also on CBS sitcom "The Royal Family" and in the comedy film "The Master of Disguise".
Zack Teperman, who called himself his former publicist, said he was shocked by the news of his disappearance.
"I still can't believe what I hear and I hope it's not true," he posted on social media. "I'm just sad. Naya Rivera was one of the first people I had the honor of working with in 2009 when I entered public relations and moved to Hollywood. One of the first people to allow me to give her advice and guide her through those crazy days of Glee. "
Rivera was previously married to actor Ryan Dorsey.
