LAKE PIRU (CBSLA) — Saturday marks the fourth day in the search for 33-year-old “Glee” actress Naya Rivera after she went missing while on a lake with her 4-year-old son in the Los Padres National Forest in Ventura County.

Search crews are expected to continue to use side-scanning sonar technology and cadaver dogs as they continue to look for Rivera across Lake Piru, which is more than two miles long and 130-feet at its deepest point.

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Capt. Eric Buschow of the Ventura County Sheriff’s office said the side-scanning sonar technology provides crews with a detailed image, which then allows them to “focus on specific things rather than putting divers in the water when they are feeling around because they can’t see.”

For now, crews will be focused in on the northern part of the lake.

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Rivera and her son took to the water in a rented pontoon boat back on Wednesday. Hours later, her son was found in the boat alone wearing his life jacket. Hers was still on the boat, however.

Security footage shows Rivera and her son moments before heading to the lake. (Ventura Co. Sheriff’s Dept.)

Investigators do not suspect foul play; security video shows the pair being the only two people aboard.

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“We don’t know if she is going to be found five minutes from now or five days from now,” Buschow said.