The first passengers have been taken ashore from a coronavirus-hit cruise ship that docked at California's port of Oakland, with the infected "being dealt with in proper isolation", US Vice President Mike Pence said.
The Grand Princess arrived in the San Francisco Bay after days stranded at sea with 21 confirmed coronavirus infections among more than 3,500 passengers and crew.
The Department of Foreign Affairs and Trade (DFAT) confirmed six Australians had been travelling on the cruise ship.
It is unknown whether any of the Australians, including two who are long-term US residents, have contracted COVID-19.
"US authorities are testing every person on board, and we are awaiting advice as to whether any of the Australians has contracted COVID-19," a DFAT spokesperson said in a statement.
Emergency workers equipped with gowns, gloves, respirators and face shields loaded those requiring immediate treatment into ambulances, while all port employees and residents were cleared from the fenced-off landing site.
Ambulances approach the coronavirus-hit Grand Princess at port in Oakland, California, to take passengers to hospital or into quarantine. Source: EPA
"We hope before the end of today to begin to disembark California residents," Mr Pence said.
More than 900 passengers from the state were on board, including 25 children who Mr Pence said were healthy.
"Individuals will be led off the ship in smaller groups," and "anyone who is symptomatic... will be fitted with a surgical mask and disembarked via a separate gangway" to avoid disease spread, said a statement from Governor Gavin Newsom's office.
DFAT said the Australian Consulate-General in San Francisco was ready to provide consular assistance to any Australian who had been on the ship.
The ship had been idling off the San Francisco coast since Wednesday.
Passengers gathered on balconies were "whooping and waving at dock workers onshore" as the ship drew into port, Carolyn Wright, 63, of New Mexico, said from on board the vessel.
Tents were set up on the Oakland quayside, with the surrounding floor doused in what appeared to be disinfectant, she added.
Buses and flights were lined up to transport passengers.
After initial screening, those who don't require acute care will be quarantined for 14 days at US military bases in California, Texas and Georgia - or flown to their home countries, in the case of foreign residents.
Those at US bases will be given private single rooms with access to private bathrooms, Pentagon spokesman Jonathan Hoffman said.
Passengers will be fully tested at their onward destination to avoid delays.
"The crew itself will push off from the dock, and they will be quarantined and observed and treated shipboard," Mr Pence said.
The entire site will be decontaminated by pressure-washing with a bleach solution once the operation is complete.
Dancing on deck
Mr Wright said earlier on Monday the mood had been lifted on board by the prospect of finally reaching land, and guests were briefly allowed to leave their cabins.
Some couples danced on deck as others walked laps around the huge ship.
"It really feels wonderful to have gotten out and stretched our legs," Mr Wright told AFP. "I feel kind of energised and happy. It just makes you feel like, OK, things are happening and things are now moving."
"Hopefully things will be smooth from here on."
Robert Kadlec, a senior Department of Health and Human Services official, said: "Our intent is to disembark about half of the passengers on the boat today and the other half tomorrow."
On Monday, the Princess Cruises company announced full refunds, scrapped on-board charges and offered free future cruises to affected passengers on the Grand Princess.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, said he would "recommend strongly" anyone with an underlying condition - particularly if they are elderly - do not go on a cruise ship.
And Canada, which had 240 citizens on the ship, became the latest country to warn people to avoid taking cruises.
The US has recorded at least 26 deaths from the coronavirus and 605 confirmed cases across 35 states, according to a Johns Hopkins tally.
