Colgan, who had arranged the weekend away as best man for his brother Eamonn, was last seen in the Veermaszter pub in the vicinity of the Beatles Platz at around 1.30am on Saturday morning.
On Tuesday afternoon Hamburg police told The Local that there had been no new developments in the case.
The St. Pauli district is a popular tourist destination due to its lively night life. At the weekend its many small bars are often heaving with party-goers.
All attempts to locate Colgan have so far been unsuccessful. He is described as 1.82 metres tall, with short ginger hair. At the time of his disappearance he was wearing a leather jacket and a grey hoodie.
Police ask people who may have clues as to his whereabouts to call on 040428656789.
A post on a Facebook group set up to help find him stated that "Liam, is the best man for his brother Eamonn Colgan and is responsible for organising the stag do to Hamburg, Germany.
"Eamonn is due to marry his fiancé Susan in three weeks time back in Scotland so we are launching an urgent appeal to find Liam."