Egyptian prosecutors have ordered the detention of four people in relation to the murder of Italian student Giulio Regeni, officials say.
They are relatives of an alleged criminal gang which officials say was behind the killing. All the gang’s members died in a shoot-out.
But Italian officials have questioned this claim amid suspicion that security forces had involvement in the case.
Mr Regeni’s body was found with signs of torture, dumped beside a road.
Italian authorities have long complained about a lack of transparency from Cairo in the investigation.
The 28-year-old Italian, who was a student at Cambridge, had been researching trade unions, a politically sensitive subject in Egypt. His body was found on 3 February, a week after his disappearance in Cairo.
Two of the suspects detained are the wife and sister of the alleged gang leader. They had been arrested in the sister’s apartment, where an official said police found a bag with Mr Regeni’s passport and wallet.
The other two are the brother-in-law and brother of the head of the gang.
All four are accused of concealing a criminal and hiding stolen goods, officials said.
On Thursday, Egypt’s interior ministry said police had found a bag belonging to the student during a raid on a flat linked to the gang. All its four members were said to had been killed in a shoot-out.
The group specialised in abducting foreigners while posing as policemen, it added.
But the claim has been criticised by Italian officials and the Regeni family, who rejected it as an “outrageous set-up”.
Human rights groups and opposition figures have speculated that Mr Regeni was killed by members of the Egyptian security forces, claims Egyptian officials have strongly denied.
“[We are] wounded and embittered by the umpteenth attempt at a cover-up on the part of the Egyptian authorities,” the family told Italian news agency Ansa.
“[We are] certain of the firmness with which our government will react to this outrageous set-up”.
On Twitter, Italy’s Foreign Minister Paolo Gentiloni said: “Italy insists: we want the truth.”
Rome’s chief prosecutor Giuseppe Pignatone said on Friday that the investigation into the murder would continue.
Mr Regeni was a PhD student at the department of politics and international studies at the University of Cambridge, and a visiting scholar at the American University in Cairo (AUC)