Security has been upped at Isle of Man Airport and the Sea Terminal following the failed terror attacks in the UK.
There has been another arrest in connection with the alert.
The latest detention - in Liverpool - brings the number of people being held to
Two were detained after being stopped on the M6 in Cheshire overnight.
Two others were picked up yesterday afternoon, after the car they were
travelling in was rammed into the terminal building at Glasgow Airport.
Chief Constable of the Isle of Man, Mike Culverhouse (pictured), is urging people to vigilant: