The incident took place on a Victoria line tube train in London.
The video shows a woman confronting a man- believed to be a stranger- after he attempted to restrain her from lunging at a friend, believed to be her son.
The woman is seen sinking her teeth into the man’s arm before he pushes her away.
The man then tells her: ‘We’re just trying to get somewhere, p*** off,’ to which the woman responds: ‘Now you’re involved.’
The man then returns to the woman and shows her the damage she caused from the bite.
At this point, a TFL employee arrives on the scene and the cameraman (a member of the public) captures the extent of the damage to the man’s arm.
The video- which was uploaded last year- has since sparked a police investigation.
The British Transport Police released a statement reading: ‘We are aware of the YouTube video, which was uploaded on 18 July 2013 and was recently brought to our attention.’
‘We believe this incident took place on a London Underground train near Kings Cross St Pancras station and we're keen to hear from any of the people involved. We are currently working to establish when the incident took place and what offences have occurred. Everyone has the right to travel without fear of abuse or threatening behaviour and BTP takes this type of offence extremely seriously.’