Australian Capital Territory police say they are baffled as to how an “untoward” tweet of a pornographic image was retweeted from their official account in what is proving to be a social media disaster for the force.

The original tweet by @KSanders0902 showed full-frontal nudity with the hashtag #ThonglessThursday.

On Wednesday afternoon, ACT police thanked Twitter users for bringing the “untoward” tweet to its attention, saying it was “not sure how it got on our page”.

Thanks to those who brought an untoward tweet to our attention. Not sure how it got on our page, but it's deleted and our account is secure. — ACT Policing (@ACTPolicing) December 31, 2014

The force deleted previously favourited tweets from @KSanders0902, whose account no longer exists. The mistake caused a flurry of reaction on Twitter.

. @ACTPolicing not sure how it got on our page??? You are the police. — Susan Metcalfe (@susanamet) December 31, 2014

Well, the social media account manager at ACT policing has a resolution to add to the list — Patrick Melaugh (@melaugh71) December 31, 2014

Hey I heard that they are projecting tweets on to the harbour bridge this NYE so just be careful @ACTPolicing — Chris Urquhart (@chrisurquhart) December 31, 2014

Ladies and gentlemen, the people we rely on for protection from domestic violence. — Ann des Landes (@Ann_dLandes) December 31, 2014

A representative of the force said the matter was now closed but it would put out a statement at a later time if need be. He said the on-call media representative for the agency was out of the office on Wednesday afternoon.