The Interislander ferry Aratere won't be refloated until the morning after running aground just outside Picton.

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Interislander general manager Duncan Roy said the vessel, with 47 people on board, departed Picton at 9.45pm Friday.

It ran aground following a steering failure.

"It was a freight-only sailing with eight commercial vehicle drivers and 39 crew on board. There are no injuries and the vessel is watertight."

Roy told RNZ the ferry was "secure" and he, along with KiwiRail's chief executive Peter Reidy, would be taking the first flight from Auckland to Picton in the morning.

The plan was to refloat the ferry on the high tide, between 8am and 10am Saturday, he said.

It would be assisted by harbour tugs, and he was confident they could do the job.

"They are the harbour tugs that we use when we are coming in in heavy winds in the harbour."

It was too early to discuss what impact the grounding would have on the company's freight in the Cook Strait, he said.

"Right now I'm totally concentrated on our passengers on board and our crew on board - that is our main focus.

Right now we're totally focussed on recovering our vessel but most importantly making sure our people are safe and sound."

Roy said he understood other ships were still coming and going from the port.

Low tide was expected in the area around 2.20am, according to MetService.

The Aratere (shown by the circle in the centre of the image) ran aground on Friday night. Photo: Supplied/Marinetraffic.com

Port Marlborough said the Harbourmaster was enforcing a 500-metre exclusion zone in the harbour and would be patrolling.

"We have mobilised our marine and pilotage teams, and the two Port Marlborough tugs which are on the water, on standby to assist as required.

"Port Marlborough is working closely with the Harbourmaster, ferry crew and relevant authorities to provide all necessary support and resources."

Maritime New Zealand said in a statement that it would be investigating the cause of the crash, which occurred about 2.8km north of Picton.

Nelson MP Rachel Boyack said it would have been a "pretty frightening" incident for those on board.

"I have heard that the Harbourmaster is on board doing checks but I'm trying to find out further information. Obviously it's a pretty concerning incident."

Boyack said she had been advised everyone on board had been given a lifejacket.

Marinetraffic.com showed the Aratere was near Pine Bay and not moving just after 11pm Friday. It was about half an hour out of Picton.

The vessel's status was "aground", the website said.

St John Ambulance said it was notified of the incident at 10.04pm.

"We ... are currently on scene with two ambulances, one first response unit, one manager and a Major Incident Support Team. There are no reports of injuries."

Transport Minister Simeon Brown said in a social media post that he had been advised there was no indication of injuries, danger to life, or danger of oil polluting the marine environment.

"The vessel is watertight. Both KiwiRail and Maritime NZ are actively dealing with the situation."

In January 2023, the Interislander ferry Kaitaki broke down in the Cook Strait and ended up drifting, resulting in a mayday call.

Tug boats had to escort the ferry, which had 880 people on board, to Wellington.

A report later found the breakdown was partly due to KiwiRail not replacing critical engine parts.

Maritime NZ has since filed a charge against KiwiRail under the Health and Safety at Work Act in relation to the incident. The maximum penalty is $1.5 million.

Earlier this year, all passenger sailings on the Interislander's Kaiarahi ferry were cancelled for several days due to a mechanical fault.

Meanwhile, a project to build two new ferries and redevelop the ports was canned by the coalition government after spiralling costs meant it was no longer economically feasible to proceed.

The project would still be $1.5 billion in the hole after 2050, documents revealed.