About two dozen passengers aboard a Caribbean cruise ship that docked in Bayonne, New Jersey, on Friday were screened for coronavirus and four were sent to a local hospital for further screening, the city's mayor said.

Mayor Jimmy Davis of Bayonne, about 10 miles from New York City, described the hospitalizations as "an abundance of caution" and said officials at the U.S. Centers for Disease Control and Prevention had indicated there seemed to be little threat. "I have been advised that the CDC considers this incident 'Below Low Risk,'" Davis said in a statement on Facebook.

Video footage showed ambulances pulling up to the docked ship and medics carrying out at least one person on a stretcher.

New Jersey currently has no confirmed cases of the coronavirus and the hospital where the four passengers were taken for screening was following "proper infection protocols," New Jersey Governor Phil Murphy said on Twitter.

Royal Caribbean, operator of the cruise ship, said in a statement it is "participating in elevated levels of guest screening" to combat the spread of the virus, the New York Post reported.

The coronavirus outbreak, which originated in the Chinese city of Wuhan, has infected more than 31,000 people and killed more than 600 people. There have been 12 confirmed cases of the disease in the U.S., none fatal.

The U.S. Centers for Disease Prevention and Control has said the risk of widespread transmission of the illness in the U.S. remains very low, but the Trump administration last week declared a U.S. public health emergency to ensure containment of the virus.