The News of the World reported that the pair were critical of some of manager Gerard Houllier's coaching staff during a team break at a Spa in Leicestershire.
Sorry isn't the hardest word: Villa defender Dunne has apologised for his conduct
'I apologise unreservedly for my behaviour on Wednesday night. It was not acceptable and I am genuinely sorry,' Dunne told the newspaper.
Collins added: 'We were wrong. This should not have happened and I apologise for the part I played.'
Apology: Collins joined Dunne in expressing his regret over the incident
The club are now due to launch a review of the incident, with a spokesman adding: 'We have launched an investigation in line with our internal disciplinary procedures.'
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