Hurtigruten chief operating office Bent Martini has stepped down while investigations continue into the Covid-19 outbreak on board the Norwegian cruise line’s ship MS Roald Amundsen.

The Roald Amundsen remains in Tromso in northern Norway where it has been since July 31, with 41 crew and 21 passengers now having tested positive for Covid-19.

Almost 400 passengers from sailings which departed on July 17 and 24 have had to go into quarantine

Four members of crew were admitted to hospital last week. Two have since been discharged, but another two crew members admitted.

Martini was aboard the ship on a family holiday when the outbreak was announced on July 31.

Hurtigruten group chief executive Daniel Skjeldam confirmed Martini had stepped down “at the company’s initiative” and “temporarily resigned” from Hurtigruten’s executive management.

Skjeldam told Norwegian media: “An investigation has been launched into the entire course of events after the outbreak of the infection and the police have launched an investigation. Therefore, we cannot go into detail now.”

Hurtigruten faces growing criticism for its handling of the outbreak after reportedly delaying its response and failing to inform passengers.

Public health authorities have suggested Philippine crew members joined the ship without Covid-tests or quarantine and Norway’s media reports police are investigating whether the company violated infection-protection rules.

Hurtigruten confirmed there had been “several deviations from the company’s internal procedures in relation to the outbreak” and announced on Friday it has hired maritime law firm Wiersholm and DNV to conduct an investigation.

Skjeldam said: “We have not been good enough and we have made mistakes.”

The company reported passengers and crew aboard two other ships, the MS Fridtjof Nansen and MS Spitsbergen, had tested negative for Covid-19.

The MS Fridtjof Nansen is in Hamburg, having disembarked passengers at the end of a two-week cruise along the coast of Norway. All 162 crew tested negative, as did 168 of the 171 passengers. Three chose not to be tested.

The MS Spitsbergen will disembark in Tromso after 70 crew and 64 passengers tested negative.

Hurtigruten has cancelled all expedition sailings until further notice. The company, which is majority-owned by UK private equity firm TDR Capital, described “the short-term financial implications” of the suspension as “limited”.

The company claimed to be the first in the world to return to ocean cruising when its MS Finnmarken re-launched on June 16.

By early July, Hurtigruten had four ships operating in Norwegian coastal waters plus expedition ship MS Fridtjof Nansen.

MS Roald Amundsen and MS Spitsbergen began Arctic expedition cruising in mid-July.

Hurtigruten planned to reintroduce seven more ships in August and September, meaning 14 ships would have been operating by the end of next month.

The world’s major cruise lines have no plans to resume before November.

Hurtigruten planned a series of MS Roald Amundsen itineraries around the British Isles in September.

The company is the world’s largest expedition cruise line.