A total of 37 crew members and 16 guests have now tested positive for Covid-19 onboard MS Roald Amundsen, according to figures from the Norwegian Institute of Public Health.
The Hurtigruten operated ship is currently moored in Tromsø, Norway, as authorities try to contain the outbreak.
Cases were first reported last weekend, with the line having cancelled all upcoming expedition sailing as a result.
Four members of the crew were admitted to the University hospital of North Norway last week.
Two have now been discharged, while another two have been admitted.
Tromsø municipality on Thursday stated that they have retested the crew and expect the number of infected to rise further.
Hurtigruten has initiated an external investigation into the outbreak.
MS Fridtjof Nansen
In better news for the cruise operator, all crew members and guests who were tested for Covid-19 onboard MS Fridtjof Nansen have been founded to be negative.
The ship is currently on her way back to Hamburg, at the end of a two-week expedition cruise along the coast of Norway.
On Monday, Hurtigruten revealed four crew members were being isolated due to “common cold symptoms”.
All four tested negative for Covid-19 on Tuesday.
All 162 crew members have tested negative.
A total of 168 of the 171 guests have also tested negative, with the three remaining guests choosing not to be tested.
“We are of course very glad that everyone has tested negative.
“We have not had any reason to suspect infection, but take all precautions.
“We are in close dialogue with the Norwegian and German authorities and follow all recommendations from them,” said vice president of global communications for Hurtigruten, Rune Thomas Ege.