NEW YORK (AP) — The first blockbuster upset of March Madness: Twitter over CBS on Selection Sunday.

The NCAA said Sunday night it is looking into how a copy of this year’s tournament bracket got leaked online during the network’s extended selection show on Sunday.

The bracket was being shared on Twitter about 20 minutes after the start of the two-hour broadcast, generating thousands of retweets as Charles Barkley fumbled around with a touch screen monitor making picks.

“We go through great lengths to prevent the tournament field from being revealed early and the NCAA took its usual measures to protect this from happening,” the NCAA said Sunday night in a statement. “Unfortunately, and regrettably, the bracket was revealed prior to our broadcast partners having the opportunity to finish unveiling it. We take this matter seriously and we are looking into it.”

CBS declined comment.

The broadcast drew wide criticism on social media for drawing out the selections. Some Kentucky players fell asleep during the show at the home of coach John Calipari. And others waiting for their draw found out about their matchups early as news of the leaked bracket went viral.

At Notre Dame, coach Mike Brey said he got a text from his son, Kyle, a tight ends coach at Youngstown State, saying the leaked bracket showed the Irish playing the winner of the Michigan-Tulsa game in Brooklyn.

“I thought he was messing with me,” Brey said. “So I just deleted it. Fifteen minutes later we show up, and then I found out we had a little leakage going on. Nothing’s secure, huh? That’s great. That is so typical. It’s so typical of college basketball.”

At Pitt, Sterling Smith set the Panthers at ease early during the selection show, sharing the leaked bracket that showed them as the 10th seed in the East Region. “We were wondering what we were going to do for that entire time; all of a sudden we knew rather quickly,” coach Jamie Dixon said.