The New York Yankees' game against the Philadelphia Phillies on Monday in Philadelphia also has been postponed because of the outbreak. Miami (2-1) played the Phillies in its first three games of the season through Sunday at Citizens Bank Park in Philadelphia.
Major League Baseball announced the schedule changes Monday morning and said the games were being postponed as the league "conducts additional COVID-19 testing."
Later Monday, MLB commissioner Rob Manfred announced that Tuesday's contest between the Marlins and Orioles was scrapped. He said if the results from the additional testing are acceptable, the teams will resume playing Wednesday in Baltimore.
The Marlins stayed in Philadelphia on Sunday night and were scheduled to fly to Miami on Monday. Instead, the Marlins chose to remain in Philadelphia.
"The members of the Marlins' traveling party are self-quarantining in place while awaiting the outcome of those results," MLB said in a statement.
"Major League Baseball has been coordinating with the Major League Baseball Players Association; the Marlins; the Orioles; the Marlins' weekend opponent, the Phillies; and club medical staffs, and will continue to provide updates as appropriate."
Marlins pitcher Jose Urena had been scheduled to start Sunday before he was removed from the rotation after testing positive. He was among four Marlins players who tested positive for the coronavirus Sunday.
Marlins CEO Derek Jeter said the team conducted another round of testing for players and the staff and will remain in Philadelphia until test results are available. The Marlins expect to receive those results sometime Monday.
"The health of our players and staff has been and will continue to be our primary focus as we navigate through these unchartered waters," Jeter said. "After a successful spring [training] 2.0, we have now experienced challenges once we went on the road and left Miami.
"Postponing tonight's home opener was the correct decision to ensure we take a collective pause and try to properly grasp the totality of this situation."
Marlins manager Don Mattingly said after Sunday's game that the team "never considered not playing" after members learned about the positive tests.
"We are taking risks every day," Mattingly said. "That's what the players all around the league are doing. You travel all the time, in planes, buses, different hotels."
Mattingly also said "it was a lot scarier" to play games on the road amid the coronavirus.
"It feels safer in Miami than anywhere," Mattingly said. "You feel safe at the ballpark and safe with my surroundings going home. It's a lot scarier on the road. You just don't feel near as comfortable.
"At home we know, we've dealt with it the whole time there. We know the places to get food and all the stuff. It's not the same."
The Marlins were scheduled to host the Orioles on Monday and Tuesday in Miami. The team is scheduled to face the Orioles in Baltimore on Wednesday and Thursday.