A passenger on board a cruise ship in Italy has been diagnosed with the common flu, Italian operator Costa Cruises said in a late Thursday statement.

Earlier, some 6,000 tourists were held on the cruise ship over fears that the ill passenger could be infected with the coronavirus.

"Sanitary protocol" had been activated amid concerns over the health of an individual traveling on the ship operated by Costa Cruises. The ship reached the Italian port of Civitavecchia on Thursday morning, where it had sailed from Palma in the Spanish island of Mallorca.

"While we appreciate the inconvenience caused, the procedures in force and our cooperation with the Health Authorities were effective in managing this situation and were intended to ensure maximum safety for all our guests, crew and the community as a whole," Costa Cruises said in its statement announcing that the passenger had the common flu.

The cruise operator had previously confirmed to CNBC that medics onboard had been alerted to a suspected case of the virus in a 54-year-old Chinese woman, who had been kept in isolation alongside her travel companion since Wednesday evening.

Late Thursday, Italy's ministry of health said that the cruise ship samples were negative.

According to The Associated Press, health officials screened 6,000 passengers and 1,000 crew members aboard the ship, and all were being prevented from leaving until the type of virus infecting the woman was determined.