Police have seized cocaine worth an estimated street value of £15m.
Cumbria police said the drugs were discovered when two lorries trying to enter the UK at the port of Harwich in Essex were stopped and searched.
Two men from Lancashire, one from Kendal and another from Nottingham are be questioned in Cumbria. Another three men have been released on bail.
The two vehicles are believed to have come from Holland and were targeted as part of a long-running investigation.
Two of the men released on police bail were from Grantham, Lincolnshire and one from Melton Mowbray, Leicestershire.
Addresses in Cumbria, Lancashire, Nottinghamshire and Lincolnshire were searched.
Police in Cumbria, Lancashire and HM Customs said drugs were only found in one of the lorries, but both vehicles were connected to the smuggling ring.
Police confirmed that one of the men arrested was a 49-year-old from Kendal and another was a 55-year-old from Nottingham.
The Nottingham man was arrested on suspicion of being involved in the importation and supply of cocaine and was taken to Cumbria for questioning.
Detective Chief Inspector Jeff Ashton, of Cumbria CID, said: "There are also on-going operations with about five other forces to trace others suspected of being involved."