A cruise ship owned by Carnival Corp. was blocked from leaving an Italian port with some 7,000 people on board, after a passenger came down with symptoms that raised concerns about a possible case of coronavirus.

Carnival’s Italian unit Costa Crociere SpA said that a 54-year-old woman from Macau is in isolation on board its Costa Smeralda cruise ship in the port of Civitavecchia, near Rome.

Preliminary medical reports indicated that the virus was not present, an Italian official said.

Carnival shares erased some of their earlier losses on the news of the medical tests, and traded down 3.5 per cent at 10:33 a.m. in New York.

Still, Civitavecchia’s mayor, Ernesto Tedesco, urged caution, calling for a continued lockdown of the ship pending full tests. The ship will be held in port for another 24 hours, Rai television reported.

The vessel is currently the only ship docked in the city’s port, with a limited security presence around it. Passengers can be seen walking on the decks, even as empty buses wait below for an eventual disembarkation. Soft jazz can be heard playing on board.

A medical team from a Rome hospital earlier Thursday examined the patient, who demonstrated fever and respiratory symptoms, according to the Italian Coast Guard. Further operations on the ship “will be decided later,” a Coast Guard spokesman said.

Prime Minister Giuseppe Conte told reporters during a visit to Bulgaria that Italy is adopting all measures to tackle risks linked to the virus, adding that “there is no need to spread alarmist information or to fuel any form of panic.”

“As soon as the suspected case emerged, medical staff on board immediately activated the necessary health procedures,” Costa Crociere said in a statement. “Our priority is to guarantee the health and safety of our guests and team.”

Italian media reported that passengers have been protesting the lockdown of the ship and lack of information.

“We don’t have information, no internet, because on the ship it doesn’t work,” Ansa new agency cited Italian passenger Liborio Iervolino as saying.

Cruise stocks have been slumping as analysts projected an earnings impact from coronavirus. Carnival and Royal Caribbean Cruises Ltd. previously suspended some cruises departing from China, a small but growing market for the U.S. companies.

Patrick Scholes, an analyst with SunTrust, said the Italian lockdown wouldn’t help.

“Even if it is a false alarm, the surrounding media attention is a negative for the propensity to book a cruise,” Scholes said Thursday by email. “Too early to quantify the financial impact from this latest news, but it’s safe to say that it will put pressure on earnings and investor sentiment.”

The vessel was bound for La Spezia in the Liguria region, with 1,000 crew and 6,000 passengers, 750 of whom came from China, a port spokesman said.

— With assistance by Sonia Sirletti, Flavia Rotondi, Tommaso Ebhardt, Chiara Remondini, Marco Bertacche, and Alessandro Speciale