Luxury French cruise ship investigated twice in one month after hitting rock in Milford Sound

L'Austral was entering the Milford Sound on Thursday when it struck an underwater object. Photo / Supplied.

French cruise ship L'Austral has come under investigation for the second time in a month after reportedly hitting a rock in Milford Sound.

The Transport Accident Investigation (TAIC) launched an investigation after the 142-metre- long ship hit an underwater object near Stewart Island in January, Fairfax reported.

The ship, one of many owned by luxury cruise company Ponant, struck another underwater object on Thursday.

The ship, one of many owned by luxury cruise company Ponant, struck another underwater object. Photo / Flickr Creative Commons

"It was entering the Milford Sounds under the directions of the pilot on board when it brushed an underwater object," said Ponant's Australian PR manager Michael Corbett.

Corbett said he assumed the object was a rock.

"There is slight hull deformation but no breach of the hull, so no water is coming into the ship," he said.

TAIC's investigation of the incident "is standard procedure," according to Corbett and won't interrupt the cruise itinerary.

Ponant operates two cruises on L'Austral in New Zealand waters, prices for which begin at A$7000 (NZ$7459).

The ship holds a maximum of 260 passengers, 132 cabins and two restaurants on board.