Nicki Minaj is said to have threatened Mariah Carey after her American Idol co-star called her a ‘b****’ – it is now being claimed. Show bosses cancelled filming in Charlotte, North Carolina for the day on Tuesday after a huge blow up between the pair where Nicki allegedly threatened and swore at Mariah. But witnesses insist Hero hitmaker Mariah started it, according to reports. A source told Mouthtoears.com: ‘Nicki Minaj walked off of set because Mariah Carey kept making jabs at her. ‘Nicki’s manager and team convinced her to come back to the show. Mariah kept at it and called Nicki a b**** and then proceeded to cuss her out. Producers had to stop filming and call it a night.’ It was previously reported how Nicki fumed she was sick of her co-star’s ‘f*****g highness’. Their fellow panellists Keith Urban and Randy Jackson were caught in the middle of the row, according to TMZ, which is running a video of the row, where Nicki can be heard ranting at Mariah. A source told the website: ‘[Nicki said to Mariah] ‘I’m gonna knock you out’ – although this was not caught on tape. In the video being run by TMZ, Minaj can be heard saying: I told them I’m not f*****g putting up with her f*****g highness over there [Referring to Mariah]. Figure it the f*** out. Figure it out.’ Mariah can also be heard answering back in the video – but it is difficult to make out exactly what she is saying. The row is said to have started due to a disagreement over a contestant’s performance.