According to a new investigation, one in three returned Islamic State fighters in Sweden have committed serious crimes after coming back from the Middle East.

The investigation, which looked into the activities of 41 Islamic State members who had returned from Syria and Iraq, found that all of those sentences or suspected of crimes, 13 people in total, were men, Swedish broadcaster SVT reports.

The crimes that the men have been either suspected or of convicted of have included serious offences such as the case of a 31-year-old man who was filmed by his neighbours attacking another man with a pair of scissors last July and is now looking at attempted murder charges.

Other offences include drug-related crimes, fraud, extortion, money laundering, abuse, and some have also found themselves in trouble due to owing taxes.

Gabriel Wernstedt, press secretary at the Swedish Security Police (Säpo), would not comment on specific cases but said they were working together with other authorities.

“The purpose is to protect Sweden and democracy. Within the framework of this mission, we follow a number of crime-active individuals within different extremist groups who have an intention and ability to commit crimes, which could, for example, be related to terrorist offences,” Wernstedt said.

The investigation comes only weeks after it was claimed that Islamic State members living in the heavily-migrant populated city of Malmö had been operating underground mosques and attempting to recruit new extremists.

“The situation here in Rosengård is really bad,” a local mother said.

Around 150 Islamic State fighters have returned to Sweden from the Middle East, but many municipalities have admitted they have no idea where they are.

In Gothenburg and Västra Götaland, for example, dozens of Islamic radicals are believed to have returned to the area, but the municipality only knew of ten adults and eight children who had returned.

With many ISIS radicals still in the Middle East, many of them arrested by Kurdish or Iraqi forces, some have requested to return to Sweden.

While other countries have stripped the citizenship of some ISIS members, Swedish prime minister Stefan Löfven ruled out the practice, saying that Swedish citizens could return but they would receive little in the way of consular support to do so.

Follow Chris Tomlinson on Twitter at @TomlinsonCJ or email at ctomlinson(at)breitbart.com