OWINGS MILLS, Md. -- The NFL canceled the Baltimore Ravens' practice for Monday morning, a day before the team is scheduled to play the undefeated Pittsburgh Steelers, a source told ESPN's Adam Schefter.

The Ravens are in the midst of one of the biggest outbreaks in professional sports with at least one positive test for the past eight days. Baltimore has officially placed 18 players on the Reserve/COVID-19 list in the past week and has since had three starters -- tight end Mark Andrews, outside linebacker Matthew Judon and wide receiver Willie Snead IV -- test positive, according to sources.

As of Monday morning, the Ravens are still deciding on when to travel to Pittsburgh, according to a source. Baltimore was originally set to take two planes, which would allow for extra social distancing, to Pittsburgh on Tuesday morning and play the Steelers at Heinz Field that night. But the Ravens could leave as early as Monday night because the Pittsburgh area is expected to get 2 to 4 inches of snow Tuesday.

The outbreak in Baltimore has already led to the Week 12 game between the Ravens and Steelers to be postponed twice.

The Ravens were about to hold their first full practice in 10 days on Monday morning before the league cancelled it. The team facility has been closed since Tuesday at noon.

After the practice was cancelled, All-Pro Ravens cornerback Marlon Humphrey tweeted: "Virtual Tuesday Night Game?"

Virtual Tuesday Night Game? https://t.co/9pVNlX0gPS

— Marlon Humphrey (@marlon_humphrey) November 30, 2020

Over that time, at least a dozen players have tested positive, including reigning NFL MVP Lamar Jackson, running backs Mark Ingram and J.K. Dobbins, starting center Patrick Mekari, fullback Patrick Ricard, defensive end Calais Campbell, outside linebackers Pernell McPhee and Judon, according to a source. All of these players will not play against the Steelers.

In total, there have been at least 30 members of the Ravens organization -- from players to coaches to even the team nutritionist -- who have tested positive or have been identified as a high-risk close contact since Nov. 22.