A sailor assigned to the amphibious assault ship Boxer tested “presumptive positive” for the new strain of coronavirus, marking the first case for a sailor on board a Navy ship and the second known patient from Naval Base San Diego.

Tests conducted by the Navy or private, county or state clinics are considered “presumptive positive” until the results are confirmed by the Centers for Disease Control and Prevention.

The sailor was treated by Naval Medical Center San Diego personnel and is quarantined at home. Personnel believed to have been in close contact with the sailor also have been ordered into self-isolation at their residences or quarters for 14 days.

None of them is living on the warship, which is homeported at Naval Base San Diego. Boxer is not at sea.

The group is believed to be less than 10 sailors now, but military health workers continue to investigate whether any additional people have been exposed to COVID-19.

Depending on the results of that investigation, additional measures might be taken.

In a prepared statement issued by the Pentagon, officials said that the Boxer’s crew continues to take “appropriate preventative measures” and is “conducting a thorough cleaning,” following guidance from the CDC and the Virginia-based Navy-Marine Corps Public Health Center.

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Although Navy Region Southwest announced Saturday that another sailor tested “presumptive positive” for the coronavirus, he is assigned to a tenant command that is not a warship.

Officials do not believe there is a connection between the two cases, but the investigation continues.

Vice Adm. Richard Brown — the Naval Surface Force commander for the U.S. Pacific Fleet — has vowed to take every measure possible to protect the force. Officials are closely coordinating with county, state and federal health authorities to protect personnel, their families and the local population, according to the statement.

Boxer’s crew assembled last month in the hangar bay to celebrate the vessel’s 25 birthday, but the sailor is believed to have contracted the disease several weeks after the event.

The San Diego County Public Health Office reported on Friday that 158 people were being monitored for potential exposure to COVID-19.

This is a breaking story and Navy Times will continue updating it.