A homeless Italian man was detained on Tuesday on suspicion of murdering 19-year-old American university student Beau Solomon, police said.
Massimo Galioto, 40, was detained overnight and was being held for questioning later in the day by a judge on suspicion of aggravated homicide, a police spokesman said, declining to give further details.
Solomon's body was found tangled in vegetation in the Tiber River on Monday, three days after he went missing.
Solomon, from Wisconsin, had been due to start a study program at John Cabot University, whose campus is in the central Trastevere district.
The neighborhood is near the river and popular with young people because of its many bars. Solomon was last seen leaving a pub early on Friday morning.
Solomon's brother Jake told NBC News that, after he went missing, their parents had called his credit card company and learned that thousands of dollars had been charged to his card in Milan, hundreds of miles away in northern Italy.
(Reporting by Philip Pullella; Editing by Kevin Liffey)