Multiple referees have been sent home from the NCAA men's basketball tournament's controlled environment in Indianapolis due to a positive COVID-19 test and contact tracing, the NCAA said in a statement Monday night.

Per the NCAA, one official tested positive on Monday and had interacted with five other officials. All six were sent home. Four of the refs have been replaced from a pool of reserves; two won't be replaced.

Stadium reported that referees Ted Valentine, John Higgins and Roger Ayers were among those sent home.

"The NCAA has replaced several officials for March Madness because of a positive COVID-19 test," the NCAA said in a statement. "One official tested positive March 15, and five other officials the person interacted with the day before were identified as exposure risks due to prolonged close contact. Based on tournament protocols and contract tracing with local public health authorities, these officials may not participate in the tournament. The infected official must be placed in isolation, and the other officials must be placed in quarantine."

The NCAA brought 60 referees to Indy in total.

While all signs point to the tournament proceeding without hiccups, a team has until Tuesday to notify the NCAA if it cannot meet its protocols for the Indianapolis bubble. It's unclear which players will be available for Kansas, which withdrew from the Big 12 tournament, and Virginia, which withdrew from the ACC tournament, because of COVID-19 issues.

If any team is forced to withdraw by Tuesday, one of the NCAA's four replacement teams -- Louisville, Colorado State, Saint Louis and Mississippi -- will be used as a substitute. After Tuesday, teams that have to withdraw will not be replaced and their opponents will advance.