'X Factor' Contestant -- Hospitalized After Bad Tuna Take Out

Tonight's "X Factor" live show is being sabotaged by tuna sub sandwiches that left several contestants vomiting -- and now one's even been rushed to the hospital ... TMZ has learned.

Sources close to the production tell TMZ, Drew from the group Emblem3 went to the set, but had to be hospitalized within the last hour because he couldn't stop heaving up his guts. We're told he's currently on an IV drip at an L.A. hospital, and may not be back for the live broadcast.

We're told the vomit-fest started last night when a bunch of contestants and crew members ordered take out to their Hollywood Hills pad -- and almost everyone who ate the tuna salad subs were up sick all night. We'll spare you the details.

Total casualties: 6 crew members out sick, Camilla from the group 1432 is on set, but yacking non-stop ... and of course, Drew is down for the count.