Jackson’s official Web site said only that the singer “was regretfully forced to cancel her performance” and that “Janet apologizes to her Milwaukee fans.”

Milwaukee TV station WTMJ reported Jackson chipped a tooth and had to undergo a root canal.

spokeswoman Michelle Kempin said Jackson’s accident occurred sometime Wednesday afternoon while they were setting up the show.

Some disappointed fans got the news Wednesday night after arriving at the downtown Bradley Center. Promoters told fans to keep their tickets because they hope the concert can be rescheduled.