A "BOMB threat" was reported on a CalMac ferry on Friday evening, shortly after a passenger was rescued after falling overboard.
All remaining services on Friday have been cancelled to allow crew to be debriefed and for emergency equipment to be replenished.
At around 8pm the police stood down their response following a search of the vessel.
The ferry operator confirmed that customers on board a service to Arran were evacuated as emergency services attend the incident at Ardrossan harbour.
All 329 passengers who were on board and those who were at the port were guided to the nearby Asda car park by police as the search was carried out.
The same vessel saw a person being reported overboard during the 4.40pm sailing of the MV Caledonian Isles from Brodick to Ardrossan at around 5.30pm.
The vessel's Fast Rescue Craft was launched and the passenger was safely retrieved. The coastguard was also alerted.
It is understood that shortly after, the "security threat" was received.
CalMac crew launched emergency protocols immediately, searching the vessel and removing passengers on foot at the earliest opportunity.
CalMac chief executive Duncan Mackison said: “This was a fast-moving situation that was handled professionally by our crew, Ardrossan port staff and emergency services and I would like to extend my thanks and gratitude to them.”
The HM Coastguard confirmed it attended an incident off Ardrossan at around 5.25pm on Friday.
Police Scotland and the Scottish Ambulance Service were also in attendance.
