Rihanna attends The 57th Annual Grammy Awards in 2015 Credit: Jeff Vespa/WireImage

Where's RiRi? R&B superstar Rihanna canceled her Grammys 2016 performance shortly before the CBS broadcast went live on Monday, February 15, sources confirm to Us Weekly. Her rep tells Us the reason for the last-minute decision was due to her health.

"Based on Rihanna's examination, after Grammy rehearsal today, Rihanna's doctor put her on vocal rest for 48-hours because she was at risk of hemorrhaging her vocal chords," her rep tells Us. "The antibiotics she has been on for 3-days did not kill the infection adequately therefore she cannot perform safely."

The songstress issued an apology via Twitter several hours after her scheduled performance. "#NAVY so sorry I couldn't be there ....." she tweeted. "Thanks Grammys and CBS for your support tonight."

The Anti singer was noticeably missing in action on the red carpet at the Staples Center in L.A., where reporters awaited her arrival. Sources tell Us that Rihanna pulled out from the broadcast suddenly.

"Rihanna dropped out a half hour before the show," one insider tells Us. "It caused a huge crisis."

According to the insider, the songstress was supposed to have performed toward the beginning of the ceremony, but things were shifted around so that the remainder of the show could go on as planned. Rihanna also missed a rehearsal this past weekend, the source adds.

Prior to music's biggest night, Rihanna was in NYC preparing for her New York Fashion Week debut with Puma. The star-studded event, held this past Friday, February 12, featured the Hadid sisters.

Can't get enough of Us? Sign up now for the Us Weekly newsletter packed with the latest celeb news, hot pics, and more!