NorthWestern Energy says about 300 gallons of mercaptan spilled near the company's gas-gathering operation near Cut Bank. Natural gas is naturally odorless, so utilities add the chemical to give the gas its sulfuric smell that alerts people to a leak.
NorthWestern officials say the chemical doesn't present any danger to the public, although people nearby will have to put up with the unpleasant odor for a little while.
The cleanup is expected to extend into Thursday evening.
