According to a source close to the Fox reality show, Matthew, 43, was fired from So You Think You Can Dance "after he had an inappropriate relationship with a female contestant," Peoplereported.
"They didn't have sex, but he reached out to her through flirty direct messages on social media," the source said.
"She felt uncomfortable with his line of comments and went to producers, who then got Fox involved. He was fired after they did their own investigation."
The source claimed Matthew and the unidentified female contestant "never met up off-set" but his messages definitely "crossed the line."
Representatives for Matthew and Fox did not respond when People requested a comment.
Late last week, Matthew had released a vague announcement that he was leaving So You Think You Can Dance that had left the circumstances of his exit unclear and left some fans believing he may have left SYTYCD voluntarily.
On Friday, just over a week intoSo You Think You Can Dance's Season 17 broadcast schedule, the Tony Award-nominated Broadway star and former Glee star issued a statement to multiple press outlets about his sudden and unexpected departure from the show.
Matthew said he was "leaving" the show, which premiered on May 18, because he "did not follow competition production protocols" during filming.
"Having the opportunity to be a judge on So You Think You Can Dance was an incredible honor for me. Therefore, it is my deepest regret to inform you that I will be leaving the show," Matthew said late last week.
"After filming the audition rounds for the show and completing the selection of the 12 finalists, I did not follow competition production protocols, preventing me from being able to judge the competition fairly."
He added, "I cannot apologize enough to all involved and I will be watching alongside you all on what I know will be one of the best seasons yet."
Given the reality dancing competition's audition episodes have already been filmed, Matthew will continue to appear on the So You Think You Can Dance season for a couple more weeks.
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Representatives for Fox toldUs Weekly on Friday that the network "will soon announce a new judge to the series for the next wave of the competition starting on June 15th featuring the Top 12 performing for America's vote."
An insider told the magazine at the time that Matthew is "disappointed" about his early exit from the series but he's "happy to have left on good terms."
"He plans to spend time with his family and is excited about what is next," the insider noted.
Matthew is married to 37-year-old Renee Puente, his wife of seven years with whom he shares two toddler children, son Revel James and daughter Phoenix Monroe.