"Her hopes are to return to the Octagon as soon as possible but for now we ask for people to respect their privacy during this time," Brian Butler-Au wrote.
ESPN's Marc Raimondi and Ariel Helwani first reported Wednesday that Namajunas was withdrawing "for undisclosed reasons."
UFC was forced to change its headliner as well after Khabib Nurmagomedov confirmed he wasn't traveling to the United States for his bout with his match with Tony Ferguson.
The company also had to find an alternate location when the New York State Athletic Commission refused to sign off on staging UFC 249 at Barclays Center in Brooklyn.
The New York Times' Kevin Draper reported UFC is moving the event to Tachi Palace Casino Resort in Lenmoore, California, which hasn't yet been confirmed. Draper noted that holding the pay-per-view on tribal land allows UFC to work around the California State Athletic Commission and avoid falling under California's statewide stay-at-home order.
UFC 249 is scheduled for April 18, with Ferguson fighting Justin Gaethje for the interim lightweight title. Raimondi and Helwani reported the promotion is still working on a replacement for Namajunas.