Authorities investigating the disappearance of Naya Rivera in a Californian lake have said that there is no suggestion that the actress committed suicide.

The 33-year-old Glee star rented a boat and took her four-year-old son Josey Hollis Dorsey out on Lake Piru on Wednesday afternoon but just hours later the boat was found adrift with the child asleep on board.

Josey is said to have told police that his mother jumped in the water for a swim but did not resurface, leading officers to presume that she has died by accidental drowning.

"We interviewed her son and there was nothing that we learned from her son that would have suggested that this was suicide," sergeant Kevin Donoghue told People. "Everything that we've learned so far leads to this being some sort of water recreational accident.

"To say definitively what actually happened, we really can't say. We just don't know, it's a mystery... We're still investigating, we're still searching. We're trying to uncover clues as we go. But so far, we really don't have a lot of information to make any guesses as to what could have happened."

The search, which involves more than 100 specialists, is poised to enter its fourth day later today.