Producers said Simon Cowell's expressions were "misinterpreted"

He was caught on camera rolling his eyes and raising his eyebrows as a contestant paid tribute to the 32 people who were shot dead on Monday.

Cowell claims he did not hear Chris Richardson's speech on stage.

"I may not be the nicest person in the world, but I would never disrespect those families or victims," he said.

Cowell, who had accused Richardson of singing in a "nasal tone", insists he was talking to fellow judge Paula Abdul about the performance when he made the face.

Executive producer Ken Warwick said Cowell was "mortified" over the accusations.

Chris Richardson is from Virginia, where the shootings took place

"He would be the biggest fool on television if he did that. And he's not a fool, believe me," Mr Warwick said.

He said noise and the microphone set-up made it difficult for Cowell to hear Richardson after his song.

In a statement, another executive producer, Nigel Lythgoe, also defended the music mogul.

"This is a sad time for everyone, so it is especially disheartening that a quick camera cutaway could have been misinterpreted," he said.

The Fox network said it had received few complaints about the incident.

Dave Burnell, the manager of WFXR, the local Fox station in Virginia, dismissed the matter as unimportant.

Show tribute

"It's just like everything. Everyone second-guesses everything these days," he said.

"The media should be concentrating on why this person did it, talking about the families affected."

At the start of the show, host Ryan Seacrest paid tribute to the victims.

"At this difficult time, we want to say to all those affected by the terrible tragedy at Virginia Tech our thoughts and prayers are with you," he said.