Police say more than 500 complaints have now been filed in connection with the New Year's Eve attacks, with about 40 percent involving sexual offenses. Germany's justice minister said the violence appeared orchestrated.
The number of cases reported to police after a night of mass sexual assaults and thefts rose to 516 on Sunday, sharply up from a previous 379.
Police said 19 named suspects were under investigation, adding that a 19-year-old Moroccan man had already been arrested on suspicion of theft of a mobile phone.
Witnesses at Cologne's main train station and cathedral on Saturday described women being groped as well as subjected to lewd insults and robbery. In one instance, a rape was reported.
Most of the culprits were said to have been of a North African or Middle Eastern appearance. The reports have fueled criticism of Chancellor Angela Merkel's open door policy on refugees and migrants, with some 1.1 million new asylum seekers registered in the last year alone.
The wave of crime on New Year's Eve was mirrored in the northern city of Hamburg, where 108 cases were filed. Offenses were also recorded in other cities, but on a much smaller scale.
'A specific date picked'
The scope and synchronicity of the attacks led German Justice Minister Heiko Maas to speculate that the sexual assaults and robberies were planned and organized in advance.
"No one can tell me that it wasn't coordinated and prepared," the minister told the popular German Sunday newspaper Bild am Sonntag. "My suspicion is that this specific date was picked, and a certain number of people expected. This would again add another dimension [to the crimes]."
The newspaper provided details from official police reports citing the use of social networks by some North African migrant communities to encourage their peers to join them in the square between the Cologne train station and the cathedral, where the now hundreds of alleged incidents of molestation and pick-pocketing took place.
Need to process data
Germany's Federal Criminal Police Office (BKA) told the Sunday newspaper "Welt am Sonntag" that it would collate information from across Germany on attacks like those in Cologne to gain an overview of the situation, which would then serve as a basis for coordinated action.
This information would then allow the systematic implementation of measures to combat the problem of sexual assaults on women carried out by groups, according to the BKA.
The paper cited the BKA as saying that it took "the events of New Year's Eve and the associated public uncertainty very seriously."
rc/gsw (dpa, AFP, Reuters)