Montana gas prices went up over the last week by about four cents. The amount may not seem like much, but gasbuddy.com Petroleum Analyst Patrick DeHaan says the trend is surprising.

"It's kind of a surprising trend that we saw such an uptick in Montana, I wouldn't say that is something that we expected, especially when compared with the national average which was actually down by about a penny per gallon," DeHaan said. "By and large, it has been kind of quiet nationally, the national average is only up about 6/10 of a penny from a month ago, but Montana has bucked that trend."

Gas prices across the state are at about $3.47. Dehaan says to expect another slight increase over the week ahead.

The cause of Montana’s rising prices remains a mystery for analysts.