The latest stop on Britney Spears' Circus tour featured a little too much smoke and not enough mirrors.

The pop star has issued an apology to ticket holders of last night's Vancouver show after smoky conditions on stage led to a 30-minute delay of the concert-a delay that came just three songs in after Spears walked off stage without explanation, leaving the crowd to sit (and boo) in the dark arena.

"The building is awfully smoky," an announcer finally explained to the sold-out crowd, per the Vancouver Sun. "It's become uncomfortable and unsafe for the performers, including Ms. Spears.