Rivera, 33, disappeared on a rented boat at a lake on Wednesday, authorities told local news outlets.
She was reported missing after a trip to Lake Piru in Ventura County. The actress and her son, 4-year-old Josey Dorsey, were in a pontoon boat and swimming the water.
Staff later found the vessel with her sleeping son on board, officials said. Rivera was nowhere to be found.
In a statement, the office said that “multiple teams of professional search and rescue personnel are actively searching Lake Piru for any clues to the location” of Rivera, who played Santana Lopez on the Fox series for six seasons.
“With over 80 people involved in the search right now, we are using helicopters, boats, ATV vehicles, and ground personnel to try and locate her. We have mutual aid for specialized dive teams en route from Los Angeles County, San Luis Obispo County, and Tulare County. We will keep you posted with any updates as we learn them. Our hearts and prayers go out the all of the family and friends of the Rivera family,” according to the statement.
Heather Morris, who worked with Rivera on “Glee,” said on Instagram that “we need all the prayers we can get to bring our Naya back home to us. We need your love and light,” including prayer emojis.
Other details were not provided.
Harry Shum Jr., who also appeared on the show, wrote on Twitter, saying “Praying.” Iqbal Thebawrote, another “Glee” star wrote on Twitter: “Oh God… mercy… please…,” while re-posting a report of Rivera’s disappearance.
Two other actors who appeared on “Glee” have died in recent years. Mark Salling, who played “Puck” on the show, committed suicide in January 2018 after he was accused of assault and possession of child pornography.
Years before that, Cory Monteith was found dead in a Vancouver, Canada, hotel room. Officials later ruled that he died of a toxic combination of heroin and alcohol.