Leeds Rhinos and Huddersfield Giants have closed their training ground as a precaution for a minimum of five days after positive Covid-19 tests.
The Rhinos confirmed six players and a member of staff had contracted the virus, while Giants report a "number" of cases in their football group.
Both facilities will undergo a deep clean before re-opening.
All positive cases and those flagged up through contact tracing are now isolating for the required 10 days.
Leeds say staff and players will be allowed to return to the training ground at Kirkstall Road after the five-day shutdown, once they have posted a negative polymerase chain reaction (PCR) test result.
This is in line with Rugby Football League protocols and as per Public Health England guidance, with both organisations informed of the decision to close up.
"It is important that we look after the well being of our people," said Leeds director of rugby Kevin Sinfield.
Giants managing director Richard Thewlis added: "We have followed the guidelines laid down precisely and quickly which meant that following this mornings lateral flow testing a threshold was hit whereby we immediately closed our facility and will take a five day break again as per the guidelines,"
Players were given the go-ahead to resume training earlier this month, with a target date of 25 March for the resumption of Super League.
Although the season was shortened and some games lost to coronavirus in 2020, Super League was able to complete the season and ensuring a safe environment to return in 2021 is a major priority.
"We have increased our bio security at Leeds from last season and everyone is vigilant about ensuring we lessen the probabilities of spreading the virus," continued Sinfield.
"Because of our increased testing since New Year, it has become evident that, despite all our precautions, the virus has continued to spread within the group. We hope this short period will act as a fire break and enable us to move forward next week."