A cruise ship being held off the coast of San Francisco Thursday due to suspicions of the new coronavirus disembarked hundreds of passengers in four Mexican Pacific ports during a cruise last month that included passengers who later tested positive for the illness.

At least three passengers on that Grand Princess cruise have been confirmed to have the new virus, and one of them became California’s first fatality from the virus Wednesday.

US health officials are scrambling to track down other passengers who have returned home. But when Mexican health officials were asked about it late Wednesday, they said they had not been notified and have announced no actions.

The Grand Princess stopped in Manzanillo, Puerto Vallarta and Mazatlan before before making a final call in Cabo San Lucas on Feb. 18 and heading back to San Francisco. The passenger who died this week in California began showing symptoms the next day, but only tested positive for the virus March 3, according to health officials.

Officials in the states where those ports are located had announced no measures on Thursday. Those in Jalisco, Sinaloa and Colima did not immediately return requests for comment.

Local tourism authorities had lauded the Grand Princess’ arrival in each port, and local newspapers published photos of passengers disembarking and shopping for souvenirs.

The port of Manzanillo published a tweet said it received the visitors “with open arms.”

Passengers typically wander port cities buying crafts, eating in restaurants and taking day excursions to area attractions, potentially putting them in contact with many locals.

Mexico so far has five confirmed cases of the disease – none of them related to cruises. But when asked about the Grand Princess case during a daily briefing Wednesday evening Mexican health officials said they were unaware.

The country’s head of epidemiology, Dr. Jose Luis Alomia Zegarra, said officials would have to look into it, adding that they had not been told about that particular cruise ship. He said they were monitoring other ships.

Alomia gave the example of another cruise ship last week that had been turned away at other ports before docking in the Caribbean port of Cozumel. He said authorities followed proper protocols in testing suspected cases and then allowing the passengers to come ashore when results showed it was the normal flu.

“For this or for any other cruise ship that could arrive the same protocol is applied, they do the same things and if no risk is identified for the country, then the passengers are welcomed to Mexico,” he said.

Baja California Sur Gov. Carlos Mendoza Davis, who was also participating in the coronavirus briefing as head of the national governors organization, spoke from the perspective of an at-risk state. He noted that Baja California Sur was in the middle of its cruise ship season, during which it receives hundreds of ships and about half a million passengers per year.

The virus could put state officials like Mendoza in the difficult position of choosing between protecting their citizens from the virus’ spread and cutting off a vital source of income for their port cities.

On Thursday, Ivan Hernandez, spokesman for Baja California Sur’s health department explained the protocol.

Health authorities maintain contact with port administrators who provide them with lists of arriving ships. Health authorities contact the cruise lines before the ships arrive to request their logs and any ongoing health issues aboard. “Based on that information, it’s verified first at a distance or digitally and later, the day they have scheduled the arrival they visit the ship to confirm the information is correct,” Hernandez said. Only then are the ship’s passengers allowed to disembark.