The search for Glee star Naya Rivera has turned into a recovery operation as of Thursday morning, and she is believed to have drowned, according to officials.

“Investigators believe Rivera drowned in what appears to be a tragic accident,” said a statement from the Ventura County Sheriff’s Office.

Rivera, 33, was reported missing on Wednesday after she failed to return a pontoon boat that she rented with her 4-year-old son Josey Dorsey on Lake Piru in Ventura County, Calif. The rental company staff went out searching for the boat when it was not returned in the evening, and found Dorsey asleep in the boat alone.

“Rivera’s son told investigators that he and his mother had been swimming in the lake, and he got back in the boat, but Rivera did not,” the statement said.

On Wednesday evening, a 50-person team spent five hours looking for Rivera, but had to pause the search as divers were experiencing dangerous zero-visibility under the water.

“The entire shoreline and surface of the lake were thoroughly searched. Divers also searched under water in the area where the boat had last been seen. However, there was no sign of Rivera,” the statement said.

On Thursday morning the search continued, though divers still had issues with only one-foot visibility in the daylight.

“The difficult conditions have made the recovery operation a very slow process,” the Ventura County Sheriff’s Office said in the statement, but they added that the Los Angeles County Sheriff’s Department has assisted in the search for Rivera with divers and sonar equipment.

“Approximately 100 personnel are participating in the mission on Thursday, including resources from neighboring counties and the United States Coast Guard,” the statement said.

The Ventura County Sheriff’s Office has also released the 911 call placed when Rivera’s son was found alone on the boat, and the security footage of Rivera arriving at the boat docks, renting the boat and driving it towards the north end of the lake.

Rivera is best known for playing Santana Lopez on Glee from 2009 to 2015, and had been married to actor Ryan Dorsey from 2014 to 2018. The couple shares custody of their son, Josey.

Rivera’s last tweet from Tuesday afternoon shows her and her son with the caption “just the two of us.”

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