Police in the Swedish capital Stockholm have launched an internal investigation into accusations that the force covered up widespread sexual assaults by mostly migrant youths at a music festival.
In a case echoing recent attacks in Cologne, a group of men reportedly groped girls at the We Are Sthlm event.
Police ejected 200 people from the site in August but did not mention assaults in their reports to the press.
Sweden was the first country to offer permanent residence to Syrian refugees.
The allegations relate to both the 2014 and 2015 editions of the festival.
Following the most recent event, a police spokesperson told local media: "There have been relatively few crimes and few taken into custody considering how many participants there were."
Varg Gyllander, head of communications for Stockholm police, admitted the force "should have communicated" details about the alleged sexual assaults.
"I actually do not know why it did not happen," Mr Gyllander told Radio Sweden. "Police have, as I understand the information I have been given, done a pretty big job there. A number of people have been removed due to harassment of women."
The omission from the police's account of the event came to light in an internal police memo leaked to newspaper Dagens Nyheter, which recorded that police identified 50 suspects and removed 200 people from the event over its five days.
The organisers of the festival, which is held outdoors at Kungstradgarden Square in central Stockholm, told the newspaper that there had been cases of sexual harassment every year, but that beginning in 2014 groups of boys and young men began to work the crowds together.
According to Peter Agren, who led the police operation at the festival this summer, the controversy over welcoming refugees and migrants to the country may have contributed to a reluctance to publicise the issue.
"Sometimes we do not really say how things are because we believe it may play into the hands of the Sweden Democrats," Mr Agren told Dagens Nyheter, referring to Sweden's right-wing anti-immigration party.
Mr Gyllander also conceded that the issue may have been a factor. He said: "These days, the level of discussion is very harsh, and it's very aggressive when it comes to discussing the matter of refugees and foreigners. I think that all of us are very careful how we express ourselves."
But he denied there had been any kind of cover up.
Stefan Lofven, Sweden's centre-left prime minister, called the incident "a double betrayal" for the women assaulted.
"We shall not close our eyes and look away. We need to deal with such a serious problem," Mr Lofven told Expressen newspaper.
At a press conference on Monday, national police commissioner Dan Eliasson said the force's conduct would be internally investigated.
"We have to get to the bottom of this. We will first hand it to the internal investigation to see if any wrongdoing or crime has taken place," he said.
Dagens Nyheter has also been accused of failing to report on the assaults, despite receiving a tip-off. Caspar Opitz, the newspaper's editorial director, wrote in a blog post that the paper took the tip "very seriously" but was unable to confirm it.
In the Cologne attacks, New Year's Eve revellers said they were groped and robbed by gangs of men , of North African or Arab appearance, at city's train station. The police response tot he attacks have been criticised.