LAS VEGAS -- The UFC lost its pay-per-view main event on the day of UFC 213.
White confirmed to ESPN that Nunes was taken to a hospital for an undisclosed illness both Friday and Saturday morning after she said she didn't feel well. He said Nunes was cleared to fight by a doctor but was pulled because "she said she didn't want to fight."
"Yesterday, she started to not feel good, so we took her to [the] hospital," White said early Saturday evening on SportsCenter. "[The doctor] did a full evaluation and she was medically cleared to fight. She weighed in at the ceremonial weigh-in [Friday] and squared off with Shevchenko, then went home last night.
"This morning, [Nunes] called again and said she didn't feel good. So they brought her back in [to the hospital] and started running tests on her, and she said she didn't want to fight ... she didn't feel good and didn't want to fight. She was medically cleared to fight, was checked and everything was fine, but she said she didn't feel right."
Shevchenko (14-2) was left without an opponent just hours before doors were scheduled to open at T-Mobile Arena. Though White said in an earlier Instagram post that Joanna Jedrzejczyk was "begging us" to let her fight Shevchenko on short notice, the fight was not made.
"I wish I was the guy that could make that happen," said White, adding that Jedrzejczyk put on a full-court blitz and even offered to sign a waiver. "It can't be done. ... Impossible to pull something off like this hours before the fight."
Jedrzejczyk and Shevchenko already fought each other three times in Muay Thai competition during their martial arts careers.
Shevchenko expressed her displeasure over the loss of a big paycheck and a long-awaited title shot in a post on her social media accounts.
"During the last three months of training, I did everything to be in my best shape for this fight," Shevchenko wrote. "Nunes couldn't cut weight correctly and was hospitalized. She wanted to cut weight and recover rapidly to have the advantage. The end result, everything went wrong. Even though she was medically cleared to fight, she backed out. ... I did my part and am very upset that I can't fight for the title today on this great event."
A member of Shevchenko's team told ESPN that the fighter still planned to be at the arena Saturday night.
During the card, Nunes took to Twitter to say she'll be back.
Sorry to all my true fans. The fight will be rescheduled and I will be back at 100%. 🦁 Essa luta vai ser remarcada e estarei 100% pic.twitter.com/8WEttqMUgM— Amanda Nunes (@Amanda_Leoa) July 9, 2017
White said he hopes to reschedule the Nunes-Shevchenko fight, "hopefully in Edmonton" on Sept. 9.
The fight was supposed to mark Nunes' second defense of her 135-pound title. She successfully made weight Friday.
The Brazilian champion overwhelmed Ronda Rousey at UFC 207 late last year, winning in just 48 seconds.
Nunes fought Shevchenko at UFC 196 last year. Nunes ran off to an early lead in the fight, but Shevchenko appeared to be making a comeback in the final round. Nunes went on to claim a unanimous decision.
It marks the third consecutive year that the UFC has been forced to cancel the main event of its annual International Fight Week show on short notice.
Last July, Jon Jones was removed from his bout against Daniel Cormier three days before UFC 200 for violating the promotion's anti-doping policy. Jones was slapped with a one-year suspension, but his rematch with Cormier is scheduled for July 29 at UFC 214 in Anaheim, California.
UFC 213 lost its likely main event for the first time in late May when men's bantamweight champion Cody Garbrandt decided his back injury wouldn't allow him to prepare for a bout against TJ Dillashaw.
The Associated Press contributed to this report.