Several ferry workers are under investigation for failing drug and alcohol tests after medication was stolen from a ship’s medical room.

Employees on Stena Line’s service between Scotland and Northern Ireland are ­understood to have been suspended or had their contracts terminated.

It follows the break-in at the end of last month on board a Superfast vessel on the route between ­Cairnryan in Wigtownshire and Belfast.

A source said: “The medical room on board the ship was broken into and controlled drugs were found to be missing.

"To find out who it was, they went on a fishing expedition and started testing the staff.

“Several members of staff were suspended on the spot.”

The Record understands that 15-20 staff were tested and about five suspended. Others had ­prescription drugs in their system.

Stena Line confirmed “a number of employees” were tested randomly on its Belfast to Cairnryan route and had failed tests.

A spokesman added: “Stena Line is now carrying out a full ­investigation as part of its ­established ­disciplinary process.”

The firm, which also said it has a zero ­tolerance policy to drugs and alcohol and insists all prescription medication should also be fully disclosed, called in police.

Police Scotland said it was aware of the incident but it was being investigated by Belfast Harbour Police because it falls under its jurisdiction.