The NCAA canceled its men’s and women’s basketball tournaments on Thursday because of the spread of coronavirus, putting an abrupt end to the season less than a month before champions were to be crowned.

The unprecedented move comes a day after the NCAA announced the games that were scheduled to start next week would go on, but played in mostly empty arenas. That plan was scrapped as every major American sports league from the NBA to MLB put the brakes on its season due to concerns about the pandemic.

“This decision is based on the evolving COVID-19 public health threat, our ability to ensure the events do not contribute to the spread of the pandemic and the impracticality of hosting such events at any time during the academic year given the ongoing decisions by other entities,” the NCAA said in statement.

The NCAA canceled all of its spring championships in every sport, which include hockey, baseball and lacrosse.

The NCAA men’s basketball tournament has been played every year since 1939 when Oregon won the championship in Evanston, Illinois. It has grown through the years, both in size and stature. The three-week tournament generates almost a billion dollars in revenue each year for the NCAA and its hundreds of member universities and colleges, most coming from a television contract with CBS and Turner that pays the NCAA almost $800 million per year.

It is now one of the biggest events in American sports, a basketball marathon of buzzer-beaters, upset and thrills involving 68 teams. The field for the men’s tournament was scheduled to be announced Sunday. The 64-team women’s field was to be revealed Monday. The NCAA women’s tournament began in 1982 and it, too, has become a big event, raising the profile of the sport.

“I’m disappointed but I totally understand. I really feel for the senior student-athletes; every student athlete, but particularly the seniors because this is their last chance for the fans,” said Oregon women’s coach Kelly Graves, whose team would have entered the tournament as favorites to reach the Final Four in New Orleans. “There’s something more important than the games going on. I’ve kind of come to grips to that a little more than a few hours ago.”

Games would have started on the men’s side on Tuesday in Dayton, Ohio, before spreading out to eight sites from coast-to-coast from next Thursday through Sunday. The women’s tournament was scheduled to begin March 20, with first- and second-round games to be played at 16 sites on or near the campuses of the top teams.

The men’s Final Four was to be played April 4 and 6 at Mercedes-Benz Stadium in Atlanta. The semifinals and final typically pack football stadiums for the games, and after the champion is crowned the best moments of the year’s tournament are wrapped up into the “One Shining Moment” montage that has become a staple of CBS’ television coverage through the years.

Instead, March Madness took on a different meaning as sports have virtually shut down.

Earlier in the day, the most powerful conferences in college sports had canceled their men’s basketball tournaments Thursday because of the coronavirus.

Within minutes of each other, the Atlantic Coast, Big Ten, Big 12, Pac-12 and Southeastern conferences announced the remainder of their tournaments would not be played. The Power Five leagues were preparing to play games in large arenas across the country, but with few people in the buildings.

From Boise, Idaho, to Birmingham, Alabama, one of the busiest college basketball days of the year — with teams fighting for championship trophies and automatic bids to the NCAA men’s and women’s tournaments — was being shut down. By mid-afternoon, 56 of 58 Division I men’s basketball games in 15 conferences scheduled for Thursday had been scrapped. Only the Mid-Eastern Athletic Conference, which had two games scheduled to be played in Norfolk, Virginia, on Thursday night had not yet been canceled.

Duke and Kansas, two of the country’s premier basketball schools, suspended all athletic competition involving their teams.

“We make the best decisions possible with the best available information available. And the NCAA leadership is going to have to make that,” SEC commissioner Greg Sankey said. “I won’t judge right now what the outcome may be. There’s a pause. They’ve got some time candidly that I did not have today, and I would encourage them to use time to fully evaluate and be thoughtful and determine whether we might be able to go forward with any of the NCAA championships in this relatively short window.”

Big 12 Commissioner Bob Bowlsby said Thursday it was “hard to tell right now whether there will be an NCAA Tournament to play in” while announcing the Big 12 was closing up.

Texas and Texas Tech were going through pregame warmups and a handful of close family and friends were already in the stands at the Sprint Center in Kansas City, Missouri, when the teams were pulled off the court 40 minutes before tip-off.

“I think this is emblematic of how our country will be responding to a very unusual set of circumstances,” Bowlsby said. “I feel good that we made the right decision for the right reasons.”

Following the NCAA’s lead Wednesday, most college conferences announced that their basketball tournaments would be conducted with limited fan access the rest of the week. By Thursday, after the NBA suspended its season Wednesday night, they decided not to play at all.

Some took a little longer than others to pull the plug. The Big East started its second-round game between top-seeded Creighton and St. John’s at Madison Square Garden in New York and not until halftime was the tournament called off.

As the Bluejays and Red Storm were playing, a few subway stops away at Barclays Center in Brooklyn, the Atlantic-10 was holding a news conference to call off its tournament.

Among the other conferences that canceled tournaments were: the American Athletic Conference in Fort Worth, Texas; Conference USA in Frisco, Texas; the Sun Belt in New Orleans; the Western Athletic Conference in Anaheim, California; the Big Sky in Boise; the Southwestern Athletic Conference in Birmingham; and the Mid-American Conference in Cleveland at an arena that is home to the NBA’s Cavaliers and is scheduled to be the site of NCAA men’s tournament games next week.

The semifinals and finals of the Sun Belt men’s and women’s tournaments were set to be played Saturday at the Smoothie King Center, where the NBA’s Pelicans play and the site of this year’s women’s Final Four.

The SEC also announced the suspension of regular-season competition for teams in all sports on campus as well as SEC championship events until March 30. The ACC suspended all athletic-related activities until further notice.

Sankey said SEC teams would have been allowed to compete in the NCAA tournaments if they were played. Kansas also clarified it would not have kept its basketball teams out of the NCAAs.

For most people, the new coronavirus causes only mild or moderate symptoms, such as fever and cough. For some, especially older adults and people with existing health problems, it can cause more severe illness, including pneumonia. The vast majority of people recover from the virus.

The Big Ten was playing in Indianapolis; the Pac-12 in Las Vegas; and the ACC in Greensboro, North Carolina, at another arena set to host NCAA men’s first- and second-round games next week.

At the ACC, Florida State and Clemson were on the floor warming up for the first game of a scheduled quadruple-header when the announcement came down that no games would be played.

Top-seeded Florida State was then awarded the league’s championship trophy in an odd ceremony with Commissioner John Swofford in a mostly empty arena.

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AP Sports Writers Dave Skretta In Kansas City, Missouri, and Teresa Walker in Nashville, Tennessee, along with AP Basketball Writer Doug Feinberg contributed to this report.