Coronavirus concerns continue to cast a shadow over Major League Baseball's build-up to a pandemic shortened season, with the Houston Astros cancelling practice Saturday as two more teams reported players testing positive for COVID-19.

The Astros opted to cancel a day's worth of training after a staff member reported potential exposure to someone who had tested positive for the virus.

"As part of MLB's testing and reporting plan, we were alerted that a staff member was potentially exposed to a COVID-positive individual outside the organization," Astros general manager James Click said in a statement.

"Out of an abundance of caution, we have cancelled today's workout.

"We are working closely with MLB and our team physicians to follow the established testing and cleaning protocols so that we can safely bring our players and staff back to the field as soon as possible."

It marked the second time this week that the Astros have cancelled training because of coronavirus concerns.

Within hours of the Astros' announcement, the Kansas City Royals and New York Yankees both announced that players had tested positive.

Yankees manager Aaron Boone said closing pitcher Aroldis Chapman will not be with the team "for the foreseeable future" after testing positive for the virus.

Boone said that the six-time All-Star was experiencing "mild symptoms but overall is doing well."

Chapman, 32, can't rejoin the Yankees until he has had two negative tests over a 24-hour period.

He had been working out at Yankee Stadium for a week but had not yet participated in the club's intra-squad games.

"We're following all protocols," Boone said. "We have not had any other positive tests (from training camp)."

The Royals announced that catcher Cam Gallagher had tested positive after participating in Friday night's intra-squad training game at Kauffman Stadium.

"To say this caught me by surprise would be an understatement," Gallagher said in a statement released by the team.

"I am asymptomatic and will continue to work as hard as I can to stay ready while I quarantine.

"The first couple of weeks of workouts have just made me that much more excited about our ballclub and I can't wait to rejoin them and compete as soon as I'm allowed."

MLB and its players union on Friday said that 83 people -- 71 players and 12 team staff -- had tested positive since coronavirus testing began last month.

Teams have been conducting workouts for the past week in preparation for the delayed and shortened 2020 season, which is due to start on July 23 -- four months after the originally scheduled Opening Day in March.