Police have linked refugees to a series of thefts committed in Cologne on New Year's Eve, but there is no indication so far that they committed the sexual assaults that have shocked Germany, the Interior Ministry said Friday.
Eighteen of the 31 named suspects in the case are asylum seekers accused of committing theft and assault of a non-sexual nature, the ministry said citing an interim police report.
The suspects include nine Algerian, eight Moroccan, five Iranian, four Syrian, one Serbian, one Iraqi, one US and two German citizens.
Police confirmed on Friday that they have arrested two men with a "migrant background" in connection with the mass assault. They were released shortly thereafter due to lack of evidence.
The men had been carrying mobile phones containing video footage of the night in question and one of them had a document with Arabic-German translations of sexist phrases, they said.
Broadcaster WDR reported that this takes the total number of arrests to nine - two on Friday, five on January 3 and two on New Year's Eve itself - though it remains unclear whether or how directly they are linked to the attacks.
News magazine Der Spiegel and Cologne newspaper Koelner Stadtanzeiger reported that several mobile phones reported stolen in Cologne on New Year's Eve have been found in refugee hostels and their vicinity.
Concerns about the case have been intensified because of the lack of clarity about what happened at the Cologne train station that night.
What is known is that a group of roughly 1,000 heavily intoxicated men gathered around Cologne's main train station shortly before midnight, indiscriminately throwing fireworks at crowds of revellers and some of them breaking away into smaller groups to encircle, sexually assault and rob women.
Although police sources have pointed to the presence of mainly North African and Arab young men at the scene, it remains unclear whether the majority were in fact committing crimes or whether they provided a welcome cover for a smaller group of highly professional criminals using sexual assault to distract women in order to steal from them.
Police have confirmed they are investigating a North African crime ring in relation to the events on New Year's Eve.
Cologne police had released a statement on January 1 stating that New Year's Eve celebrations had been conducted "peacefully" and only released information about the crimes more than a day later, prompting allegations of a cover-up.
Citing unnamed police unionists, Koelner Stadtanzeiger reported that police actively withheld information about the identity of the suspects so as not so inflame xenophobic tensions in Germany.
Politicians from across the political spectrum were pushing for a security crackdown and more severe punishments for the perpetrators.
Chancellor Angela Merkel said through a spokesman on Friday that all facts in the case would have to be known before decisions could be made about consequences for the perpetrators.
"It is important to the chancellor that the whole truth is laid out on the table and that nothing is withheld or sugarcoated," deputy spokesman Georg Streiter said, adding that hasty decisions would be detrimental to the "large majority" of innocent refugees seeking asylum in Germany.
Vice Chancellor and Social Democrat leader Sigmar Gabriel told mass circulation newspaper Bild on Friday that existing laws needed to be applied to the fullest extent in order to send criminal asylum seekers back to their country of origin.
A document to be published at the party conference of Merkel's Christian Democratic Union (CDU) on Friday proposes the introduction of random police checks across Germany in order to preempt similar crimes in the future.