The coronavirus testing involves a mix of passengers and crew. The ship is carrying 3,533 people, including 2,422 passengers and 1,111 crew. In total, they represent 54 nationalities.
US health officials earlier identified those who need to be tested before the ship is allowed to dock.
The number is fewer than 100 and includes all in-transit passengers from the prior cruise, after which two people were later found to have the virus. One died in a California hospital, the first person in the state to succumb to COVID-19.
Others to be tested are those who have experienced flu-like symptoms on the current cruise and those currently under care for respiratory illness.
USCG air drops testing kits
The US Coast Guard dropped sampling kits to the ship via helicopter on Thursday morning. Grand Princess is currently making its way toward the San Francisco Bay area.
The Princess Cruises medical team is administering the test and samples are going in batches by helicopter to a lab in Richmond, across the bay from San Francisco.
No confirmed cases on board so far
Princess said there are currently no confirmed cases of COVID-19 on board. Time will tell.
As earlier reported, Grand Princess will not be allowed to dock and disembark passengers until test results are received.
March 7 cruise canceled
The ship's March 7 Hawaii cruise has been canceled. Pasengers will receive a full refund and a 100% future cruise credit.