Scratch-and-sniff cards prompt natural gas scare, evacuation

(CBS/AP) GREAT FALLS, Mont. - It's Wednesday morning, May 8, 2013.

The smell of gas is in the air. Several buildings in Great Falls, Mont., are evacuated.

Fire crews and other emergency personnel respond to the scene. They discover the culprit.

Boxes of scratch-and-sniff cards, which are mailed by the local energy company, Energy West, to teach customers to recognize an artificial smell added to natural gas.

Emergency over.

Energy West general manager Nick Bohr tells the Great Falls Tribune that workers recently discarded several boxes of expired scratch-and-sniff cards in the city. But when the garbage truck picked them up and compressed the load Bohr says "it was the same as if they had scratched them," and people feared potential danger from natural gas.

According to CBS affiliate KRTV,  fire officials determined the smell appears to have been caused by  crushed cans of mercaptan - that's the non-toxic chemical often added to natural gas to make it easier for people to detect a gas leak.

Bohr says the company apologizes for the disruption.