Dutch officials have identified 30 war crimes suspects, including 10 Syrians, among tens of thousands of asylum seekers who arrived in the country last year, the justice ministry said Monday.

Immigration authorities found the 30 after investigating 170 people, Deputy Justice Minister Klaas Dijkhoff told parliament in a letter following questions from MPs.

Ten of the suspects were from Syria, while the others are from Eritrea, Nigeria, Sudan and Georgia, he said.

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Under the Geneva Convention, refugees can be refused asylum “when serious grounds exist to believe that they are guilty of war crimes, crimes against humanity, or other non-political serious crimes,” Dijkhoff said.

But 20 of them could not be sent back because of ongoing wars or fears of inhumane treatment.

A similar Dutch investigation in 2014 identified 50 war crimes suspects, even though the number of refugees reaching the country was much lower.

The Netherlands took in 58,800 migrants last year, almost double the number which arrived in 2014 as Europe grapples with its worse refugee crisis since World War II.

The issue is polarizing Dutch society and boosting the popularity of the far-right populist MP Geert Wilders and his Freedom Party.

Several anti-immigrant demonstrations have turned violent, with refugee centers attacked and damaged.