The actor’s 4-year-old son was discovered alone in the boat they had rented on Lake Piru, in the Los Padres National Forest, on Wednesday afternoon, officials said.
The mother and son had been swimming, and Rivera never returned to the vessel, the boy reportedly told investigators.
Drones, dive teams and helicopters scoured the reservoir for the 33-year-old actor on Wednesday. On Thursday, members of law enforcement said they believe Rivera drowned and that the search is now a recovery operation, CNN reports.
“We’re presuming that an accident happened and we’re presuming she drowned in the lake,” Ventura County Sheriff’s Deputy Chris Dyer said at a news conference, per CNN.
Rivera had posted a photo of herself and her son on social media shortly before her disappearance. Her son, who was asleep and wearing a life vest when he was found, is “in good health,” according to the sheriff’s department.
Officials said the boy was in the care of family.
Multiple teams continued to scour the lake for Rivera on Thursday afternoon.
Officials said the search operation had been hampered by poor underwater visibility in the lake due to trees, plants and other debris.
“Our hearts and prayers go out the all of the family and friends of the Rivera family,” the department tweeted.
This post has been updated with details of the recovery operation.
Dominique Mosbergen contributed reporting.