The drugs were found in the rudder shaft of the 170,000-dwt Cape Maria (built 2005), operated by Empire Bulkers, in the River Clyde.

The haul, worth tens of millions of pounds, was discovered after a major operation led by the UK's National Crime Agency (NCA).

The ship was searched on Friday as it waited to dock at Hunterston after arriving from Colombia.

Police have also arrested three men at the nearby Seamill Hydro Hotel near Ardrossan and seized diving equipment, a rigid inflatable boat and an underwater scooter.