10/05/2008 AT 07:00 AM EDT
has postponed three more shows because of an undisclosed illness that had her hospitalized
The singer, 42, postponed a Saturday-night show in Greensboro, N.C., after a local doctor said it was "evident" she had not fully recovered, Jackson's publicist said.
Other shows put on hold were Sunday's in Atlanta and another on Tuesday in Fort Lauderdale. Jackson – who is on her first North American tour in seven years – previously canceled concerts in Boston and Philadelphia on Wednesday and Thursday.
A notice from
the organizers of the Greensboro gig suggested fans "hold on to their tickets pending a future announcement regarding the rescheduled date."