An Interislander ferry briefly broke down in the Cook Strait today and drifted while en route to Picton from Wellington.

Marine traffic tracking showed the Aratere was drifting about 1.8 knots this evening, outside of the route into the Marlborough Sounds.

Harbourmaster Jake Oliver confirmed he was notified of an issue with the Interislander’s Aratere ferry after 6pm when the ship was southeast off the Tory Channel.

“There was an issue which is under investigation but the ship has restored power,” Oliver said.

It’s not clear what caused the breakdown, but the ship was doing about one knot.

“Which could be a drift or a slow movement ahead - certainly not steaming ahead,” Oliver said.

The ferry is now making its way to the northern entrance of Queen Charlotte Sound.

It is understood it will be taking a modified route.

Interislander executive general manager Walter Rushbrook said the Aratere experienced “a technical issue causing a partial loss of power on the way to Picton this evening and slowed for short time”.

“She was quickly back to normal speed and has continued to Picton via the Northern Entrance of the Marlborough Sounds.

“We will be investigating the cause of the issue.”

The breakdown comes just weeks after a different ferry in the Interislander fleet, Kaitaki, also broke down in the Cook Strait.

In the late afternoon of January 28, KiwiRail advised Maritime New Zealand the ferry had reported engine problems.

Ten minutes later the ship issued a mayday call with 864 people on board. All four engines had shut down in the middle of a roaring southerly in the Cook Strait.

KiwiRail has since revealed this was caused by a leak in the engine cooling system, which resulted in a loss of pressure.

A mass rescue plan was activated when the mayday call was put out, and a special response team was stood up.

Six vessels made their way to the scene - the Interislander’s Aratere ferry, Lady Elizabeth IV, two harbour tugs, a pilot boat, and a fishing boat.

Five rescue helicopters were called, three of which were brought to Wellington Airport and two were on standby in Palmerston North and Taranaki.

Police were in charge of the onshore operation to find and take care of passengers and crew if necessary.

A cordon was put in place at Owhiro Bay Pde leading towards Red Rocks.

Wellington Cross Country Vehicle Club, one of the largest 4WD clubs in the country, was called in to help.

The independent audit of Kaitaki is not scheduled to take place until the end of this week, and the timing for its final completion is yet to be confirmed.

In the meantime, it can only carry freight, not passengers.