The search for missing Glee star Naya Rivera has yet to locate the actress, but will continue despite difficult conditions, authorities say.

Rivera, 33, was reported missing on Wednesday after taking a trip to Lake Piru in Ventura County, Calif., with her 4-year-old son, who was found alone in a pontoon boat the actress had rented. Her son reportedly told investigators that they had both been swimming in the lake, but Rivera did not get back into the boat. Investigators believe Rivera drowned and she is currently presumed dead, according to the Ventura County Sheriff's Office.

The search has been hampered by poor visibility underwater, with divers having to search by touch due to murky waters, debris, and vegetation. Ventura County Sheriff’s Department Capt. Eric Buschow reiterated this during a press conference on Friday, noting that visibility in the water is only "one to two feet."

"We know everybody's concerned about this case, and locating her, and providing some closure for her family," Buschow said. "These [situations] are difficult because we don't know if she's going to be found five minutes from now, or five days from now."

"Sophisticated sonar equipment" was brought in to aid the search on Friday, according to the Ventura County Sheriff's official Twitter account. Buschow said the sonar was being used more extensively than divers at this point, but added that the level of equipment and personnel involved would vary over the next few days.

The VCSD also released security camera footage from the Lake Piru boat launch, showing Rivera and her son arriving to rent the boat, departing the dock, and traveling north on the lake. It does not appear to show Rivera getting out of the boat.

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