A dozen officers, who are supporting policing the G7 summit in Cornwall, are self-isolating following a positive Covid test.
One person in their work bubble provided a positive lateral flow test on Friday morning.
The team were being accommodated on a ferry in Falmouth, but have since been moved to a designated isolation area.
Devon and Cornwall Police said the next stage is for those with positive results to undertake a PCR test.
A spokesperson added: "As part of our testing regime, during the early hours of 11 June one officer who is currently supporting G7 policing and accommodated on the ferry, has given a positive lateral flow test for COVID-19.
"The officer, plus those who have come into close contact, are currently self-isolating at another designated location.
"We are continuing to follow the advice of Public Health England."
More than 5,000 officers, on top of 1,500 from the force, are helping police the summit of world leaders.
Police had hired the cruise ship to accommodate officers working during the summit.
The MS Silja Europa is being used for the event between 11 and 13 June.
The ship, which usually sails around the Baltic Sea, is moored off Falmouth.
The G7 summit is being held in Carbis Bay and more than 4,000 rooms in separate accommodation, such as hotels, were also booked by the force.