The 33-year-old was reported missing on Wednesday afternoon when her boat was seen drifting at Lake Piru, while her son, 4, was found asleep on board by a rescue team.
Currently, the foreign media has recorded a series of CCTV footage showing her arriving at the boat for the last time.
Rivera and her son had rented a boat for three hours to Lake Piru in Los Padres National Forest at around 1.00 p.m.
However, when the Mother and son had not returned by 4:30 p.m., workers had gone to search for them.
The boy told authorities that he and his mother had been swimming in the lake, and said he got back in the boat but his mother did not.
According to media reports officials have searched the lake for over five hours on Wednesday night and continued on Thursday, but have not found Rivera.
Approximately 100 people are involved in the search which continues.
She became more popular through a music program called Glee and was best known for playing cheerleader Santana Lopez in Glee, the hugely popular musical comedy TV series that ran on the Fox network from 2009 to 2015
Rivera, who portrayed cheerleader Santana Lopez on "Glee," was nominated for a Grammy in 2010 as part of the cast who sang a rendition of Journey's "Don't Stop Believin.'" She also won several ALMA awards, a People's Choice Award, and a Screen Actors Guild Award.
She was recently on a boat trip with her son on Piru Reservoir in northeastern Los Angeles when she died in an accident.
However, the foreign media further reports that their bodies have not been found yet.
The relevant CCTV footage is given below.