Glee star Heather Morris has asked if she can help with the search for her missing co-star Naya Rivera.

More than 100 specialists are now working on the search and recovery of Rivera, 33, who is thought to have drowned in California's Lake Piru on Wednesday afternoon.

Morris and Rivera developed a lasting friendship while working together on Glee and in a Twitter message to Ventura County Sheriff's Office, Morris offered her services to help with a foot search around the lake.

"My name is Heather Morris, I'm Nayas close friend and co-worker, and I'm trying to conduct an on foot search and rescue mission along with a small group of friends at Lake Piru," she wrote.

"I understand your team is doing EVERYTHING in their power, but we are feeling helpless, powerless and want to help in any way. I have left a message with the department of Rescue and Air today, and I will call again tomorrow. Thank you."

Rivera's mother, father and brother paid an emotional visit to Lake Piru on Saturday as the search continued.