The singer hurt herself during a dance routine toward the end of her show Thursday night in Moline, Ill. Spears was singing one of her new songs, "Boom Boom," according to "Entertainment Tonight."
"Entertainment Tonight," like CBSNews.com, is part of Viacom.
Minutes later, the syndicated television program reported, the 22-year-old pop star reappeared on stage in a white bathrobe and apologized to the audience for not being able to continue. She'd planned two more encore songs.
Spears' label, Jive Records, said in a statement that she'd have to cancel Friday night's concert at the Allstate Arena in Rosemont, Ill., in suburban Chicago. Ticket holders were told to keep their tickets until further notice.
About 15,000 fans were expected at Friday's concert, Allstate Arena marketing director Phil Chihoski said. He said the venue hoped Spears would reschedule a performance for sometime in April.
Jive representatives weren't immediately available for comment Friday afternoon.
Spears is in the midst of her "Onyx Hotel Tour," which runs through the summer.