Five P&O Ferries staff have been suspended amid allegations rules around alcohol and drugs have been breached.
The company confirmed the action was taken pending an investigation into claims the strict policies had been "contravened".
No other details have been revealed, but a source claimed the five worked on the ferry Pride of Canterbury.
P&O's Pride of Canterbury ferry
They also said another four staff on the Pride of Kent were being investigated, but the company has confirmed that it only involves five staff.
For many years, P&O Ferries have enforced strict rules on staff about drinking alcohol and taking drugs.
Safety of the ships and passengers has been paramount and crew members as well as land-based staff have been left in no doubt about the consequences of breaching the rules.