German police arrested seven Afghan asylum-seekers while raiding refugee shelters last week, accusing the gang of raping an Iranian teenager multiple times. Authorities said the seven refugees also filmed the assault.

Over 30 officers raided several shelters in Nagold and Wildberg towns in Baden-Wurttemberg state in southwestern Germany.

Germany, which took in nearly 900,000 refugees last year, has witnessed several acts of violence in its overcrowded refugee shelters, which typically don’t have much space or privacy. Women and children residing in these shelters face a heightened threat of sexual assault, aid workers said.

“The Afghan asylum seekers are suspected of having raped a 17-year-old Iranian asylum seeker several times and of having filmed the acts,” Baden-Wurttemberg  police and prosecutors reportedly said in a joint statement.

In July, a 17-year-old Afghan refugee was shot dead by police after he attacked passengers on a train with an axe and a knife. Three of the victims were seriously injured, one suffered minor wounds and 14 people were treated for shock.

Meanwhile, Berlin is mulling over deporting at least 40,000 of the nearly 79,500 Afghan refugees currently in the country who have applied for asylum. Authorities are working on a deal with Kabul in which asylum seekers who want to return to Afghanistan voluntarily and those who have been denied asylum thrice in a row will be deported, the Russia-backed RT network reported in September, citing Germany’s Bild magazine.

Germany’s Federal Office for Migration and Refugees said 57,058 refugees had been granted asylum in August 2016, a sharp rise compared to 16,769 in August 2015.