The Pittsburgh Penguins opened training camp Monday after voluntarily sidelining nine players who may have had secondary exposure to a person testing positive for COVID-19.

The Penguins did not reveal which players were held out as a precautionary measure. The NHL has barred teams from revealing injury or illness information as a way to protect player privacy.

The players in question were potentially exposed to an individual who had contact with a person who tested positive. The players will not be allowed to practice until they are deemed safe following further test results based on NHL protocols.

All teams opened camps Monday in preparation for the NHL's 24-team playoffs, scheduled to open in two hub cities — Toronto and Edmonton — on Aug. 1. Players had until Monday evening to elect to opt out of competition without penalty.

The Penguins are the Eastern Conference's fifth-seeded team and scheduled to face the 12th-seeded Montreal Canadiens in a best-of-five qualifying round series in Toronto.

The NHL announced that 43 players tested positive for the coronavirus from June 8 through the end of the league's optional workouts. The league said 4,934 COVID-19 tests were administered to more than 600 players. Of the 43, 30 tested positive at team facilities and the others tested positive outside the NHL's Phase 2 protocols.

All players who tested positive self-isolated.