Atheists in the Okanagan are looking for answers after two ads questioning the existence of God mysteriously vanished from the side of two Kelowna buses.

The ads were bought by the Centre for Inquiry, a group representing atheists, agnostics and secular humanists and read, "There probably is no god, now stop worrying and enjoy your life."

Guy King, a spokesman for the centre, said the ads were professionally removed while the buses were locked up in the B.C. Transit yard and he's yet to receive an explanation from either the transit company or the advertising agency how that happened.

"This ad has appeared all over the world and as far as I know, there has never been a problem. This is unprecedented. No ad has ever been taken down like this before," said King.

According to reports, some bus drivers have been refusing to drive the buses with the ads, King said.

B.C. Transit representatives have been unavailable for comment on Thursday morning.

The ad campaign, which is modeled after a similar campaign in London, is set to roll out across the province over the next few weeks. Similar ads were rejected in Nova Scotia, but have run in Calgary.

After the ads ran in Calgary, a group calling itself "God Exists" purchased its own bus ads to counter the message.