Pop band Liberty X were forced off stage after a smoke canister was let off just two minutes into their concert at a university.
Liberty X found fame through the ITV talent show Popstars
The band were singing their Children in Need hit A Night to Remember at the May Ball in Aberystwyth on Saturday.
A cloud of smoke engulfed the university's venue and the band and 1,000 students had to be evacuated.
People were allowed to return after 50 minutes but Liberty X failed to reappear.
Firefighters were called to the university's arts centre where the annual May Ball, the highlight of the students' union social calendar, was being staged.
Revellers had paid £37 to see the five-piece band, as well as Bodyrockers, X-Factor's Tabby Callaghan and Chesney Hawkes.
Aberystwyth Guild of Students' commercial manager Steve Pickup said: "What appeared to be a smoke bomb was set off in the crowd near the stage and near the band's tour manager."
Andrew Austin, 22, a university student originally from Neath, witnessed what happened.
"They were just two minutes into their first song when the smoke bomb went off," he said.
"There was a lot of coughing and a few screams and a huge cloud of smoke. The smoke became so dense you couldn't see the stage or Liberty X.
"We were told they wouldn't reappear and a few people jeered, but the final act, Chesney Hawkes, did a good job."
Geraint Edwards, the guild's events manager, said it was appealing for information about the perpetrator.
"I'm more annoyed with the individual for doing something so reckless," he said.