A bus firm has launched an investigation after an image emerged of one of its drivers appearing to engage in an indecent act. 

The photo, which has been circulated widely on social media, supposedly shows a First bus driver dressed in a high-visibility jacket receiving oral sex next to a parked bus. 

It is believed the picture was taken in Atlantic Avenue in Sprowston which is on the 11 and 11A Pink Line. 

Eastern Daily Press: The image appears to show a man engaging in oral sex by the side of a First busThe image appears to show a man engaging in oral sex by the side of a First bus (Image: Manor Park Sprowston Facebook)

The 11 service uses the same recently introduced electric buses as seen in the image - which clearly shows the bus is part of the Norwich fleet.

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A First East of England spokesman said: "We are aware of the alleged incident and the matter is under investigation."

Modern double-decker buses have up to 12 cameras that face inside and out but it is unknown if the cameras were running at the time or if First possesses any footage. 

The image was posted in the Manor Park Sprowston group on Facebook by an anonymous user on Friday evening.