The latest batch of test results takes the overall figure to around 130, with the exact numbers yet to be confirmed.
More than 2,500 passengers still on the Diamond Princess are confined to their cabins and many are likely to face further tests.
Health authorities are also scrambling to deliver medicine requested by passengers with the ship expected to remain in quarantine in Yokohama until February 19.
Japanese health minister Katsunobu Kato said the government was considering testing everyone on board.
That would require them to remain on the ship until results are available, which can take several days.
Japan initially screened all 3,711 passengers and crew last week after an 80-year-old passenger who left the ship in January was confirmed to have the virus.
Nearly 300 people were selected for further tests because they showed symptoms or had contact with known patients, resulting in 61 initial positive tests.
Since then, the tests have expanded to those who had contact with the infected passengers, producing a spiralling number of confirmed cases.
Today officials said around 60 more cases had been found, saying they were double-checking the figures and could not yet confirm the exact number.
The confirmed virus patients include British honeymooner Alan Steele, who was separated from his wife Wendy and taken to the mainland on Friday.
Passengers who remain on the ship have been asked to stay inside their cabins and allowed only briefly onto open decks.
They have been asked to wear masks and keep a distance from each other when outside, and given thermometers to regularly monitor their temperatures.
The ship is expected to stay in quarantine until February 19, two weeks after the isolation period began.
The quarantine has made life on board the ship difficult, particularly for those in windowless interior cabins.
The health ministry said today that around 600 people on board urgently needed medication, and around half received supplies over the weekend.
The Diamond Princess has mostly been anchored in Yokohama Bay where workers in protective suits have delivered supplies on smaller boats.
However, it has also returned to the open sea periodically to collect seawater which can be turned into shower or drinking water.
New supplies of wet wipes and heavy-duty filtration face masks were also delivered to the passengers today.
On board the ship, news of the additional infections sparked worry for some, with passenger Yardley Wong voicing fears of ‘stress and high anxiety’.
‘I need to cry to get off the anxiety,’ she said.
Others sat in their cabins watching the Academy Awards, which were broadcast live on Monday morning.
There are 26 confirmed cases of the new virus in Japan apart from those on board the ship.
The global death toll from the virus yesterday rose to 910, all but two of them in China, after 97 people died on the deadliest day of the outbreak so far.
The virus is believed to have emerged in a market selling wild animals in Wuhan last year before spreading across China.