Two-19-year-old American tourists have confessed to killing an Italian policeman, authorities have said.
Mario Cerciello Rega, 35, was investigating the theft of a handbag in Rome when he was stabbed to death.
It is alleged the two tourists stole the bag of a drug dealer after they were given a "different substance" instead of cocaine, an anonymous Italian investigator said.
The two unnamed Americans demanded €100 and a gram of cocaine in return for the bag.
The alleged dealer called police, saying he had arranged a meeting with the thieves to get his bag and mobile phone back.
Mr Rega turned up at a meeting point organised for the exchange, where a fight broke out and he was stabbed eight times. He was taken to hospital but died shortly after.
Police used CCTV to track the suspects, which led them to a hotel room near to the scene where the Mr Rega was killed.
Police said the suspects were "ready to leave" Italy when they were found.
A search of the room found a long knife, possibly used in the attack, hidden behind a panel in room's ceiling. Police also said they found clothes the two apparently were wearing during the attack.
The Carabinieri statement said the two Americans admitted responsibility after being questioned by prosecutors and faced with "hard evidence."
It was not known if the Americans had an Italian lawyer.
Carabinieri Lt. Col. Orazio Ianniello said Saturday the suspects weren't being immediately named because they have no criminal records.