Naya Rivera’s four-year-old son told police he watched her disappear beneath the water at the California lake she is feared to have drowned in.
Police told the PA news agency that Josey Hollis, who is safe and well, saw his mother disappear under the waves during their boat trip on Wednesday.
There is no evidence to suggest Rivera, 33, left Lake Piru, Ventura County Sheriff’s Office sergeant Kevin Donoghue said.
He was speaking in response to an online petition, which has attracted almost 25,000 signatures, demanding the search be extended beyond the lake.
Sgt Donoghue said: “Our first day was a rescue effort, it was a life-saving effort.
“We searched with people on the ground, on the shoreline. We were looking not just for her physically, we were looking for any clues, any evidence that suggested she made it to shore.
“We didn’t find any clues, any evidence that suggested she made it to shore. The most conclusive piece of evidence we’re really holding on to right now is the statements from her son, the only witness.
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“He observed his mother disappear beneath the water. So we are very confident she is in the water and that at some point in time we will recover her from the lake.”
Josey was found asleep and alone on the boat while wearing a life jacket. An adult-sized life jacket was also found on board.
Sgt Donoghue added: “If we thought for a moment that there was any chance she could be on land somewhere, if we had any other clues or corroborating information that led us in that direction, we would do that and we would be out there searching and looking.”
Rivera, best known for playing a high school cheerleader on musical-comedy series Glee, is feared to have drowned at Lake Piru – a popular spot for swimmers about 56 miles northwest of central Los Angeles.
CCTV from the dock shows her rented boat departing at about 1pm and it was later found drifting in the northern area of the lake at around 4pm.
Side-scanning sonar systems, which are towed along the water by boats, have been scanning the bottom of the lake for any objects that resemble a human body.