Security at the Bråvalla music festival has confirmed at least 11 sexual assaults so far of young girls, three of which have led to arrests, and one rape was reported on Friday.

Police say they have detained and interrogated three suspects in the sexual assault cases, but have not released any information on their backgrounds or identities, Swedish broadcaster SVT reports.

Organisers of the festival, which has previously seen performances by Kanye West, Robbie Williams, and Iron Maiden, have confirmed they have called off next year’s event due to the series of sexual assaults.

The prosecutor said those arrested in relation to the sexual assaults had been released after questioning and did not say whether any charges were being considered, though they said investigations were still ongoing.

Festival safety manager Ulf Bowein was asked why the sex attacks were continuing to happen despite the increase in the number of personnel and tighter security precautions. He said: “That’s a good question—ask those who commit the infractions instead.”

“Unfortunately, it’s like anywhere in the community. We have a number of individuals who commit the crime,” he added.

Bowein noted the number of attacks had gone down in number since last year. Reports claimed that men, largely described as being of “foreign origin”, had sexually molested up to 40 girls at the festival.

The news prompted British band Mumford and Sons, who headlined the event, to announce a boycott for future performances until the situation was brought under control. The band did not feature at all in this year’s event.

Sex attacks became common at Swedish festivals last year, so much so that officials estimate the number of sex attacks at outdoor music festivals increased by 1,000 per cent in 2016.

The targets of the sex attacks are generally young girls, many of them underage. 17-year-old Alexandra Larsson was one of the victims and she described what happened to her: “First, someone touched me on the butt a few times. I turned around and inquired who had done it, but got no answer.”

“This was repeated several times. Finally, someone touched me on the genitals. Then I got angry and turned around and shouted, ‘Whoever it was, you are an idiot!'”

Festivals are not the only locations for sex assaults as various reports have shown that girls in Sweden have been attacked in railway stations, and even in public schools.