R&B icon Janet Jackson has postponed yet more concerts of her current Rock Witchu Tour due to the undisclosed illness which had her enter a Montreal hospital last week.

Janet Jackson, 42, was in Montreal last Monday, performing a sound check before the night’s concert, when she suddenly felt ill and was taken to a local hospital. The nature of her condition was not revealed at the time and no further details have been released in the meantime.

She left the Royal Victoria Hospital in Montreal after a couple of hours, a spokesperson for the medical facility said then. She did not perform that night and cancelled two more shows, one in Boston, scheduled for Oct. 1 and one in Philadelphia, scheduled for Oct. 2.

Her publicist said at the time that she needed time to recover and that she would be in Greensboro, N. C. on Saturday, Oct. 4, as planned.

The plan nevertheless changed, although not for lack of effort on Jackson’s part. She arrived in Greensboro hoping to entertain her fans as promised but a local doctor who checked her said it was “evident” she was not ready for such an endeavor, the singer’s publicist said.

Saturday’s concert was therefore postponed, as was Sunday’s in Atlanta and another one initially scheduled for Tuesday in Fort Lauderdale.

This is Jackson’s first North American tour in seven years, following the very successful tour she held in support of her 2001 album “All For You.” The Rock Witchu Tour kicked off on Sept. 10 in Vancouver, Canada, to enthusiastic reviews.

Another show was cancelled in late September, in Detroit, due to “production constraints.”

Jackson’s representatives are asking fans to hold on to their tickets while organizers try to reschedule the concerts.

The singer has had other health problems this year. In March, she dropped out of a scheduled “Saturday Night Live” performance because she had the flu but did not offer many details.

The Rock Witchu Tour is in support of her latest album, “Discipline,” which was released in February and bowed at No. 1 on the Billboard 200, her sixth studio effort to date to accomplish the feat. It has sold some 415,000 copies to date in the U.S., receiving generally positive reviews from critics.

The current tour is the fifth of her career. There has been speculation that the strenuous rehearsals and fatiguing shows took their toll on Jackson’s health. A source close to her longtime boyfriend Jermaine Dupri told People magazine last week that Jackson had complained of exhaustion.

Her representatives have said Jackson is currently “recuperating” and that she will return home for further treatment.