A Cardinals staff member and two players have tested positive over the last two days. Right-hander Ryan Helsley and outfielder Austin Dean are the identified players, according to Mark Saxon of The Athletic.
The league elected to postpone the entire series "out of an abundance of caution."
Earlier in the day, it was reported that the Cardinals were hit with only one new positive test.
With the Cubs series delayed, the Cardinals have now had 10 consecutive games postponed due to the outbreak.
If the Cardinals are able to return to the field on Monday for a series against the Pirates, the club will still need to play 55 games in 49 days in order to complete a full, 60-game schedule.
The Cubs are next scheduled to play on Tuesday in Cleveland against the Indians, and will fly back to Chicago on Friday night, according to Gordon Wittenmyer of NBC Sports Chicago.
The Cardinals recently completed a six-day quarantine in a Milwaukee hotel after a COVID-19 outbreak infected 13 members of their traveling party, including catcher Yadier Molina and shortstop Paul DeJong. These players remain quarantined at their homes. The latest tests bring their total to 16 employees hit by the coronavirus.
St. Louis hasn't played since July 29 and was about to start a stretch of 55 games in 52 days before Friday's postponement.