Just three songs and 15 minutes into a concert in Vancouver on Wednesday night, Britney Spears stopped a concert and walked off stage, citing smoke in the air.

After a delay of about half an hour, Spears returned to the stage and finished the concert. When she finished the show, she thanked the crowd and reminded them to not smoke.

In statement released on her website, a spokesperson for Spears apologized for "the brief pause it Britney's set. "Crew members above the stage became ill due to a ventilation issue."

Rolling Stone and other websites say marijuana smoke was the problem.

Smoking indoors is banned in B.C.

Celebrity blogger Perez Hilton, who is covering the tour, quotes Spears as saying at the end of the show, "Thanks Vancouver. You were wonderful. Drive safe. Don't smoke weed!"

While the show otherwise went off without a hitch, the break drew howls of derision from the audience.

Some fans were put off by the delay and left General Motors Place.

"I drove four hours to be here," said one fan from Kelowna told CTV News after leaving the show early. "This concert's not worth it."

The Globe and Mail reviewer said the show "... may have been billed as the Circus tour, but freak show would have been a better moniker for this bizarrely un-engaging, ugly production..."

Spears is currently on tour to promote her new album Circus and has also played in Edmonton, Toronto and Montreal. It's scheduled to run through June, but there are reports that Spears' management team is exploring extending the tour and going to Australia.