UPDATED 8.30pm: The Interislander ferry Aratere has been cleared to sail at 10.45pm tonight.

Its Wellington-to-Picton run this afternoon was cancelled after a number of alarms were triggered on the control screen in the engine room.

Ferry operators KiwiRail says they've since traced it to a fault in the alarm system cause by vibrations.

It says a permanent modification to reduce the risk from vibration is being discussed with the manufacturer.

Meanwhile passengers have been transferred onto alternative sailings.

KiwiRail says the disruption to passengers and freight will be cleared by mid day tomorrow .