Egyptian prosecutors ordered the detention of four relatives of the head of an alleged criminal gang that police said was found with belongings of slain Italian student Giulio Regeni, judicial sources said Saturday.

The gang leader’s wife, brother, sister, and brother-in-law were held, accused of concealing a criminal and hiding stolen goods, the sources said. Police have said they found Regeni’s possessions at a house belonging to the sister.

A judicial source told Reuters local prosecutors dealing with the gang case requested senior prosecutors handling Regeni’s death add the questioning of the four relatives to their case file.

Egypt’s interior ministry said Thursday the gang, whose four members were killed in a police shootout, had Regeni’s bag and passport in their possession. The group specialized in impersonating police and kidnapping foreigners, it said.

But the statements of the police and the ministry have failed to satisfy Italian investigators, politicians and Regeni’s family.

Chief Rome Posecutor Giuseppe Pignatone said Friday the investigation into Regeni’s killing would continue.

The broken body of the 28-year-old Cambridge University student, who was researching independent labor unions, was found at the side of a motorway on the outskirts of Cairo in February.

Human rights groups have said torture marks on Regeni’s body indicated he died at the hands of Egyptian security services, an allegation the government has strongly denied.

The case has caused friction between Egypt and Italy, though it is unlikely to lead to a permanent rift because of the two countries’ economic ties and Egypt’s strategic role in the Middle East.