"Following the Dodgers' victory, it is clear that Turner chose to disregard the agreed-upon joint protocols and the instructions he was given regarding the safety and protection of others," MLB said in a statement Wednesday.
"While a desire to celebrate is understandable, Turner's decision to leave isolation and enter the field was wrong and put everyone he came in contact with at risk. When MLB security raised the matter of being on the field with Turner, he emphatically refused to comply."
Major League Baseball was informed of Turner's positive test partway through the Dodgers' 3-1 Game 6 victory over the Tampa Bay Rays at Globe Life Field and told the team to remove him from the contest. Turner left during the eighth inning and stayed isolated until after the game, when he came onto the field and was later shown taking a picture with his teammates while not wearing a mask.
Dodgers manager Dave Roberts, who was diagnosed with cancer in 2010, was seated directly to Turner's right and was also not wearing a mask. People with preexisting conditions are considered to have a higher risk of developing serious COVID-19 symptoms.
Turner, along with his Dodgers teammates, was in MLB's so-called "soft bubble" for the NLCS and World Series. It is unclear how he contracted the virus.
Manfred told Bob Nightengale of USA Today that the sport is launching an investigation into the matter.
"We really don't know yet. I prefer not to speculate," he said. "It's important for us to trace obviously what the health situation is, and whoever was in the hotel, before turning them loose to travel.
"It's important to know, if we can, how it happened so that we're confident if we need to do this again [stay in the bubble]."
Members of the Dodgers traveling party are set to remain in Dallas to undergo further COVID-19 testing.