Heather Morris, who worked closely with Rivera on Glee, has pleaded to join the search.
The search for Rivera is ongoing after she disappeared while boating with her 4-year-old son Josey in California. Her son was found on the boat, and Rivera is presumed to have drowned.
In May, actors Michele had worked with spoke out about her behaviour. The allegations were sparked by Glee star Samantha Ware after she replied to Michele's tweets in support of Black Lives Matter.
Ware said Michele made her time working on the Glee set "a living hell".
"I BELIEVE YOU TOLD EVERYONE THAT IF TOU [sic] HAD THE OPPORTUNITY YOU WOULD 'S*** IN MY WIG!' AMONGST OTHER TRAUMATIC MICROAGGRESSIONS THAT MADE ME QUESTION A CAREER IN HOLLYWOOD," Ware posted.
Issuing a statement, Michele wrote she was sorry for her past behaviour.
"While I don't remember ever making this specific statement and I have never judged others by their background or colour of their skin, that's not really the point. What matters is that I clearly acted in ways which hurt other people," she posted.
"We all can grow and change and I have definitely used these past several months to reflect on my own shortcomings."
Although she apologised, more of Michele's co-stars came forward, issuing cryptic comments about their experiences working with her, Page Six reports.
Matthew Morrison, who played Glee club coach and teacher Will Schuester on the show, spoke about the allegations on FUBAR Radio's Access All Areas.
"I honestly think it's a distraction of the bigger issues that are going on right now," he said on the show.
"You want to be a good, pleasant person to be around," he said. "That's all I'm going to say on that.
Rivera had referenced working with Michele in her 2016 memoir Sorry Not Sorry, according to US Weekly.
"I don't hate Lea, and I never have," she reportedly wrote.
"I think [she] didn't like sharing the spotlight. She had a hard time separating work from our outside friendship, whereas it was a lot easier for me ā¦ Lea was a lot more sensitive, though, and sometimes it seemed like she blamed me for anything and everything that went wrong."