Cologne’s police chief has been removed amid criticism of his force’s handling of a string of New Year’s Eve assaults and robberies.
Wolfgang Albers is being sent into early retirement by the state government, Cologne police said.
More than 100 women reported being sexually assaulted in the city's main square in front of the main railway station. Up to 1,000 men were alleged to have been involved in the assaults and a string of robberies.
Victims had alleged their attackers were North African in appearance. Police say they have identified 31 suspects, 18 of whom are asylum seekers. None of the 31 is currently suspected of committing sexual assaults.
Cologne police said they had received a total of 170 criminal complaints related to New Year, including 120 of a sexual nature.
Witnesses reported being unable to find police, with some saying they were understaffed.
Wolfgang Albers faced mounting calls for his resignation for his handling of the affair, and has now been removed.
North Rhine-Westphalia’s governing cabinet will formally discuss the decision on Tuesday but Mr Albers will not return to his job, they said.
Cologne mayor Henriette Reker suggested that police had held back information from her, and said in a statement that her “trust in the Cologne police leadership is significantly shaken”.
Interior ministry spokesman Tobias Plate said the arrested suspects were nine Algerians, eight Moroccans, five Iranians, four Syrians, two Germans and one person each from Iraq, Serbia and the United States.
In addition to the 31 suspects detained by federal officers, city police arrested two men from North Africa, aged 16 and 23.
Police said the attacks on women were committed by small groups of men who were among some 1,000 people described as being of “Arab or North African origin” that had mingled with revellers in front of Cologne’s main train station and Gothic cathedral.
The incident has triggered calls for tighter immigration laws, particularly from politicians opposed to chancellor Angela Merkel’s open-door policy that allowed nearly 1.1 million refugees to enter the country last year.