The major NCAA conferences have cancelled their postseason basketball tournaments amid continued fears over outbreaks of the coronavirus.

The ACC, SEC, Big Ten, Big 12, Pac-12, American, MAC, Atlantic-10, Colonial, Conference USA and WAC all decided to end tournaments Thursday morning before games began in their respective arenas.

The Big East tournament quarterfinal between Creighton and St. John's started at noon ET, but the league then cancelled the entire event at halftime.

"We understand that this decision will be disappointing to our student-athletes and coaches who have been preparing all season to compete in this event as well as viewers at home," SEC Commissioner Greg Sankey said in a statement. "While this was not an easy decision, the health and well-being of our entire SEC community is of paramount importance."

In lieu of the tournament, the SEC will award its regular-season champion, Kentucky, the league's automatic bid to the tournament. Likewise with the ACC, which gave its bid to top-seeded Florida State.

“Following additional consultation with the league’s presidents and athletic directors, and in light of the continued conversations surrounding the fluidity of COVID-19, the Atlantic Coast Conference will immediately cancel the remainder of the 2020 ACC Tournament," the ACC said in a statement.

"We are disappointed for our student-athletes, schools and fans to have to make this decision; however, the overall health and safety of all involved is the priority.”

The ACC, Big East, Big 12, Big Ten, SEC, Pac-12 and other leagues had played games earlier this week and were scheduled to continue through the weekend.

The American called its cancellation “a proactive decision to protect the safety, health and well-being of our student-athletes, coaches and staff and all involved in the tournament.”

The mass cancellations place the onus on the main men’s and women’s NCAA tournaments, which remain scheduled to begin on March 17. The NCAA announced on Wednesday that tournament games would proceed as planned with spectators limited to “essential staff and limited family attendance.”

The SEC also announced it was suspending competition in all sports on SEC campuses and all championship events through March 30, but that is not a firm return date, Sankey said.

In addition to the basketball tournaments, the Big 12 said all conference championships were suspended until April 15, impacting scheduled events in women's gymnastics and equestrian.

“After consultation with our Board of Directors it was decided that cancelling these championships was in the best interest of the health and safety of our student-athletes,” commissioner Bob Bowlsby said in a statement.

The ACC later Thursday announced it was stopping all athletics activities until further notice, putting schools' participation in the NCAA tournament and other championships in doubt.