"There's no evidence to say she left the water. It appears to be 100 percent just a tragic drowning," Ventura County Sheriff's Office Sgt. Shannon King tells PEOPLE

Authorities have widened their search for Naya Rivera, though they have yet to find the actress, who disappeared on July 8 during a trip to Lake Piru with her young son.

“In today’s search for Naya Rivera, cabins and outbuildings in the surrounding area will be checked once again, as well as the shoreline,” the Ventura County Sheriff’s Office shared on Sunday. “This has been part of the ongoing search effort since her disappearance on Wednesday afternoon. Boat crews continue to scan the lake.”

Speaking with PEOPLE on Sunday, Sgt. Shannon King confirmed that investigators completed a search of the cabins near Lake Piru to make sure “nothing has changed.”

“They’re not occupied. Nothing came of it,” King tells PEOPLE, explaining that the larger focus of the search “was the shoreline.”

“They were just doing the shoreline to make sure nothing has changed. There were a lot of folks that were talking on social media about, ‘Oh, check the cabins. Maybe she’s there, maybe she’s hanging out,’ ” King says, noting that since they had “extra” search and rescue personnel on Sunday, they “did go to a couple of the cabins that were on the north end of the lake, that’s all that’s out there, and nothing came of it.”

Naya Rivera
Lake Piru
| Credit: Amy Sussman/Getty Images

At this point, authorities still have no reason to believe that Rivera ever “left the water.”

“There’s no evidence to say she left the water. It appears to be 100 percent just a tragic drowning,” King explains.

As the search for Rivera continues, authorities will continue using scanning sonar, dive boat crews and search and rescue teams for “visual surface checks” of the water.

Detailing the conditions of Lake Piru, which have complicated the search, King says “it’s not like typical waters, which are crystal clear, this is murky, cold lake water.”

Naya Rivera
Naya Rivera
| Credit: David Livingston/Getty Images

“The ground is covered in trees and shrubs, so it’s hampering our efforts for sure. So they have to go very slowly, so when they see the sonar vision coming back on their screen, the slower they go, the clearer it is,” King says. “The faster they go, the more elongated it becomes and harder to tell.”

Investigators will continue to search the area “at least through Tuesday.”

“There’s no talk of either one way or the other after Tuesday,” King notes. “Tuesday’s sort of the projected date that we’re discussing, and we’re going to continue doing what we have been doing.”

Naya Rivera; Josey Hollis
Naya Rivera and son Josey
| Credit: Gregg DeGuire/Getty Images

Rivera was presumed dead on July 9, one day after her 4-year-old son Josey was found alone on a pontoon boat at Lake Piru, where they had been swimming.

Authorities have said that Josey is "in good health" and the child has since been reunited with his dad Ryan Dorsey, who is Rivera's ex-husband. The toddler told investigators that his mother never got back into the boat after they had been in the water, according to a press release.

Documenting their underwater search for Rivera, authorities shared video footage of their efforts on July 10, which highlighted the low visibility on the floor of the lake.

"Unfortunately, they did not locate Naya Rivera. They are still searching," Ventura County Sheriff's Office Captain Eric Buschow told reporters at a press conference. "We don’t know if she’s going to be found five minutes from now or five days from now."