MIAMI -- Miami Marlins CEO Derek Jeter blamed the team's coronavirus outbreak on a collective false sense of security that made players lax about social distancing and wearing masks.

Infected were 21 members of the team's traveling party, including at least 18 players. None are seriously ill, Jeter said Monday, and he expects all to return this season.

With more than half of the team sidelined, Jeter said the Marlins still can be competitive when their season resumes Tuesday at Baltimore after a hiatus of more than a week.

Following an MLB investigation, Jeter said, it's impossible to know where the first Marlins player became infected or how the virus reached their clubhouse. They left South Florida last week to play two exhibition games in Atlanta, and then they opened the season with a three-game series in Philadelphia, where the outbreak surfaced.

"Guys were around each other, they got relaxed and they let their guard down," Jeter said. "They were getting together in groups. They weren't wearing masks as much as they should have. They weren't social distancing. The entire traveling party got a little too comfortable."

Jeter said his players were annoyed by speculation that reckless misbehavior was to blame.

"Our guys were not running all around town in Atlanta," he said. "We did have a couple of individuals leave the hotel. We had guys leave to get coffee, to get clothes. A guy left to have dinner at a teammate's house. There were no other guests on-site. There was no salacious activity. There was no hanging out at bars, no clubs, no running around Atlanta."

By Sunday, the outbreak had become so serious that the Marlins' season was temporarily suspended, with the team stranded in Philadelphia. The infected players have since returned by bus to South Florida, where they are quarantined.

"We have a lot of players who are asymptomatic, and we have players who are showing mild symptoms," Jeter said.

He said he is optimistic his players will closely adhere to the MLB virus protocol the rest of the season.

"We've been given an opportunity to hit the reset button," Jeter said. "I hope people look at what happened to us and use that as a warning to see how quickly this is able to spread if you're not following the protocols 100 percent."