United Airlines flight UA971 from Rome to Chicago was diverted to Shannon Airport in Ireland on Monday, following "a potential security concern," the airline said.
The 207 passengers and 11 crew members disembarked the Boeing 767-330 at Shannon Airport at 2:15 p.m (1315 GMT), according to Jim Molloy, a representative of Ireland's police force.
The passengers were in the process of being searched, he said in an emailed statement.
"Additional security screenings will be performed on all customers and baggage, and we will work to get customers on their way to Chicago as quickly as possible," United said in a statement.
"After assessing the situation our crew made the decision to divert to the nearest available airport," it said.
United declined to detail the specifics of the incident.