Police special op triggered in Cologne after shots fired near main railway station

German police have deployed a Special Forces unit to central Cologne following a shooting incident that took place near the central railway station. At least one person found in possession of a firearm was detained. Up to three other suspects might be on the run, according to German media. Police have raided a nearby residential building where some of the people involved might have been hiding. There have been no reports on any people killed or injured. Some reports, citing police, suggest the incident might be linked to a row between biker gangs.