A Singapore-flagged container ship is in trouble once more off New Zealand, a month after losing power.

The 5,117-teu panamax Shiling (built 2005) issued a distress signal after going adrift again off Farewell Spit on Friday in heavy seas.

The vessel had been forced to undergo tests and had only just been repaired after breaking down off Wellington on 17 April.

After the latest incident, a tug reached the ship by late afternoon local time.

Helicopters and a Defence Force Hercules plane have also been sent to the site 22 nautical miles (40 km) offshore.

A Defence Force spokesman told the New Zealand Herald that the mayday was issued at 1100 local time and the crew of 24 had been preparing to abandon ship.

“Since the mayday call, conditions on scene have improved and the vessel master has stated he is currently comfortable staying on the vessel,” he added.

The container ship’s technical manager is Asian-Alliance Ship Management (ASM) of Singapore.

ASM confirmed the vessel experienced main engine failure during passage to Singapore.

The manager requested assistance from local authorities after efforts to restore power were unsuccessful.

“Our priorities are to ensure the safety of the crew and the vessel and to protect the marine environment. All crew are safe and accounted for, and there have been no reports of pollution,” the company said.

“ASM is working closely with the local authorities and emergency service providers to bring the situation under control. A full investigation will be carried out to understand what happened and the necessary steps to prevent recurrence,” it added.

The plan is to tow the ship to a safe location. There was said to be no danger of the boxship running aground.

The Shiling had needed a tow from two tugs to move it back to its berth in April.

Wellington harbour master Grant Nalder said at that time he had “concerns about the reliability of the ship”.

Local authorities have also expressed worries over the initial incident.

“How long is our luck going to hold?” Greater Wellington Regional Council chairperson Daran Ponter said.

He questioned whether the harbour tugs could have held the ship in bad weather.

AIS data showed the panamax as not under command on Friday.

The vessel is owned by DP World’s Feedertech.

The ship is entered with the Swedish Club and has had no port state control detentions on its record since 2014.