Two young American tourists have allegedly confessed to killing an Italian paramilitary policeman after being arrested in connection with murder.
A detention order obtained by Italian state broadcaster RAI names the two suspects as Gabriel Christian Natale Hjorth and Finnegan Lee Elder.
The order says they were both born in San Francisco in 2000.
Both are suspects in the fatal stabbing of 35-year-old officer Mario Cerciello Rega after a drug deal went wrong. They are also being investigated for attempted extortion.
Elder's lawyer Francesco Codini said his client exercised his right not to respond to questions during a detention hearing held on Saturday in the Rome jail where the two teenagers are being held.
The judge has not ruled if they will be kept in jail beyond an initial three-day period.
In a statement earlier on Saturday, the Carabinieri said the Americans demanded a 100 euro (£90) ransom and a gram of cocaine to return a stolen bag.
The alleged dealer called police, saying he had arranged a meeting with the thieves to get his bag back.
Police say there was a scuffle at the rendezvous site and the policeman was stabbed eight times, dying shortly afterwards in hospital.
The Carabinieri said video surveillance cameras and witnesses allowed them to quickly identify the two Americans and find them in a hotel near the scene of the killing.
In a search, the Carabinieri said they found a long knife, possibly the one used to attack Mr Cerciello Rega.
The Carabinieri statement added that the two Americans admitted responsibility after being questioned by prosecutors and faced with "hard evidence".
