The 20-year-old singer became 'affectionate' with Ora, 23 causing the end of the couple's relationship, reported Female First.
"Word got back to Calvin, Justin and Rita got cosy with each other while they were in the recording studio together over the last few months," a source said, adding that Harris heard they were very affectionate.
Ora moved in with Harris, who produced her new track 'I Will Never Let You Down', but he has now had her belongings removed from his home.
"He's already had her things removed from his LA house ... He (also) produced a few songs for her, but now he won't allow their release," the source said.
"To address speculation - myself and Rita ended our relationship some time ago. She is a beautiful, talented woman & I wish her all the best. (sic)," he wrote.