OWINGS MILLS, Md. -- The Baltimore Ravens on Saturday said they were informed by the NFL that "at least four unique strains" of COVID-19 were found inside their facility during the team's outbreak.

"Three of the four were stopped and not spread within our organization," Ravens president Dick Cass said in a statement. "Unfortunately, the fourth was a highly-contagious strain and spread throughout our organization."

The outbreak in Baltimore was one of the biggest in professional sports.

At least one Ravens player tested positive for 10 straight days as Baltimore placed 23 players on the reserve/COVID-19 list during that span.

"From the outset, we have taken the virus seriously, very seriously," Cass said. "... Despite our best efforts, the protocol is only as effective as our weakest link. With a dangerous virus like this, everyone must comply with the protocol to avoid infecting many. We now know that not everyone at the Ravens followed the protocol thoroughly."

The Ravens recently announced a staff member had been disciplined. According to a source, the team's strength and conditioning coach was suspended for not always wearing a mask and contact tracing device in the facility.

The outbreak forced the Ravens-Steelers game to be postponed three times.

The Ravens, who have had four straight days without a positive test, reduced its reserve/COVID-19 list to 10 players on Saturday.

"We cannot undo what has occurred," Cass said. "But, we can do our best to learn from what has happened and be vigilant moving forward to ensure that it does not happen again. As the recent experience has shown us, this virus does not need a large opening to spread within an organization, and 99% compliance is not a passing grade when dealing with this virus."