Rivera, 33, was last seen swimming in California’s Lake Piru with her four-year-old son, Josey Hollis.
He was found sleeping on a hired boat soon after their rental time had come to an end.
“Show some respect,” Riley, who played Mercedes, wrote. “All our energy is going toward helping find Naya and praying for her safe return and for her family.”
Riley then addressed reports that Lea Michele had deleted her Twitter account after being trolled for failing to post about Rivera.
“No one owes anyone online a performance of grief,” she stated. “This is very real and devastating. Focus on Naya and her family. Not us. We don’t matter right now.”
McHale, who played Artie in the series, added: “I cannot begin to understand what Naya’s family must be feeling,” he wrote. “Please respect her family & their privacy in this moment. Please refrain from judging those who don’t show their pain on social media.”
The search for Rivera, who is presumed drowned, has been underway since Wednesday (8 July).
She played Santana in the series for all six seasons from 2009 to 2015.
Lake Piru is a popular spot for swimmers based around 56 miles from central Los Angeles.
CCTV from the dock on the lake shows Rivera’s rented boat departing from the shore at about 1pm on 8 July. It was found drifting in the northern area of the lake at around 4pm.
Ventura County Sheriff’s Office sergeant Kevin Donoghue said there is “little to no evidence” to suggest the actor returned to the boat.
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