"Yesterday evening she was checked into the Royal Victoria Hospital and left a couple of hours later," People quoted Rebecca Burns, the spokeswoman for the McGill University Health Centre, which operates the hospital, as saying.
However, Burns refused to divulge any details on the singer's condition, under patient confidentiality rules.
The singer's publicist also released a brief statement claiming that Jackson "is recuperating," but did not reveal her ailment.
Meanwhile, Jackson's shows scheduled for Oct 1 in Boston and Oct 2 in Philadelphia have been scrapped. However, she is expected to be back on stage for her Rock Witchu trek on Oct 4 in Greensboro, N.C.
A source close to boyfriend Jermaine Dupri revealed that Jackson has complained of exhaustion.
"A 42-year-old body can't handle what a 22-year-old body can. I can tell you that she's definitely tired. It was probably exhaustion. She is doing back-to-back, three-hour shows, and her body isn't the same as it used to be," said the source.
However, Dupri was spotted in New York City partying at Patron's Music in Motion Tour featuring TI at Marquee, on the same night that Jackson was rushed to the hospital.
"If [Janet's condition] was more serious he would've rushed to her side," added the source.