Grand Princess had been due to dock in San Francisco on Wednesday (4 April) but remains at sea while Covid-19 tests are carried out.
It comes after a passenger on an earlier Grand Princess voyage died from the infection, while several others fell ill.
California governor Gavin Newsom said 11 passengers and 10 crew members had reported symptoms.
Princess has confirmed groups of guests and crew are being tested for the infection, but stressed there have been no confirmed cases among guests currently cruising onboard Grand Princess.
The line said on Thursday (5 March) samples were collected from 45 people onboard Grand Princess, a mixture of guests and crew, and sent for testing by the California Department of Public Health.
There are currently 3,533 people onboard Grand Princess, 2,422 guests and 1,111 crew, of 54 nationalities. The Press Association reports 142 of those onboard are UK nationals, 121 guests and 21 crew.
“There are fewer than 100 guests and crew identified for testing, including: all in-transit guests, guests who sailed the previous Mexico voyage and remained onboard for the current Hawaii voyage; those guests and crew who have experienced influenza-like symptoms on this voyage; and guests currently under care for respiratory illness.
“Public health officials have advised no guests will be permitted to disembark until all results have been received. Out of an abundance of caution, all guests who have been identified for testing have been asked to remain in their staterooms.
“Guests are receiving meal deliveries in their staterooms by room service, and additional television and movie options have been added to in-room programming. Guests have also been provided complimentary internet service to stay in contact with their family and loved ones, and the ship’s internet bandwidth has been increased.”
Princess has cancelled Grand Princess’s upcoming Hawaii cruise, which had been due to depart on 7 March.
The line has also temporarily revised its cancellation policy for cruises and cruise tours departing up to 31 May, which it said was to help guests make decisions about their holidays as the global coronavirus situation continues to evolve.
For cruises departing 3 April or earlier, any guests cancelling up to 72 hours before sailing will receive future cruise credit for 100% of their cancellation fees.
Those due to travel between 4 April and 31 May who cancel by 31 March will also receive future cruise credit for 100% of their cancellation fees.
Guests with cruises from 1 June to 30 June, meanwhile, will have their final payment moved to 60 days before departure rather than 90.
Any guests who choose to retain their booking for departures from 9 March to 31 May will receive $100 per cabin for three-day and four-day cruises; $150 per cabin for five-day cruises; or $200 per cabin for cruises of six days or longer.
