The Ventura County Sheriff’s Department was still searching for Glee actress Naya Rivera as of Sunday afternoon.

The authorities have not found Rivera, who disappeared on July 8 after renting a boat on Lake Piru with her 4-year-old son. Authorities continue to believe that Rivera drowned, but have searched cabins in the area around the lake to see if there was any sign of the actress.

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

Authorities have also used cadaver dogs, divers and sonar to search the lake, but low-visibility and depths up to 100 feet have made the search challenging. The sheriff’s department shared a video on Twitter on Saturday that showed how hard it is to see in the lake via a remote-controlled camera-equipped searching device. The water is murky and trees and shrubs line the bottom of the lake, making it hard to see more than a few feet in front of yourself under the water.

The Ventura County Sheriff’s department has also warned fans to not show up at the lake to try to help.

One of Rivera’s costars and real life friends, Heather Morris has offered to help authorities search for her missing friend, but said that she “will hold off on the citizen search and rescue until we get the go ahead.”

“Understand it’s 110 degrees here and if you’re not highly trained in search and rescue, this could end up a much more dangerous situation for everybody involved,” she said. “Please be kind, compassionate and caring for those who are looking for our Naya.”

Rivera, 33, was last seen on Wednesday July 8 after renting a pontoon boat with her son, Josey Dorsey. 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. The 4-year-old told investigators “he and his mother had been swimming in the lake, and he got back in the boat, but Rivera did not,” according to a statement by the sheriff’s department.