Because of COVID-19 concerns within the Washington Nationals, their season-opening series against the New York Mets has been postponed.

Per MLB Network's Jon Heyman, Major League Baseball is postponing the series to conduct more contact tracing and follow-up tests.

ESPN's Jeff Passan added the Nationals have four people dealing with COVID-19 issues.

The Mets and Nationals were supposed to open the season on Thursday, but MLB.com's Jessica Camerato noted a positive COVID-19 test within the Washington organization caused the game to be postponed.

Camerato noted two additional positive tests came back on Thursday, bringing the total number of cases to three.

“We don’t want this thing to spread any further,” Nationals general manager Mike Rizzo told reporters on Thursday. “We want to make sure that everybody’s healthy.”

MLB health and safety protocols for this season require any individual who tests positive for COVID-19 to isolate for "a minimum of 10 days" and receive clearance from MLB's Joint Committee and team doctors, followed by a cardiac evaluation and determination that the person isn't at risk of infecting others.

Since the Nationals are still undergoing testing and contact tracing, no timetable has been announced for them to open the season.

The Mets don't have any coronavirus concerns at this time. They are scheduled to begin the regular season on Monday against the Philadelphia Phillies at Citizens Bank Park.