MISSOULA, Mont. -

Missoula police said if it weren't for a good Samaritan who saw a man throw a firework out of a truck window, there could have been a serious fire Saturday.

Police said it happened Saturday afternoon on Expressway and Martindale in Missoula.

Police said two men were driving east on Expressway in a brown Ford F-250 truck, with a tan Bronco hard roof top.

A witness said the passenger threw the firework out, and the witness went out and stomped out a fire that started.

It's an area filled with dry grass and weeds.

"With everything as dry as it is," said Detective Sgt. Scott Pastian,"it's very hard to contain a fire this time of year."

Police said the men in the vehicle were in their mid 20's.

Pastian said they could face possible arson charges.

If you have information call Crimestoppers at 721-4444 or call Missoula Police.