Gas prices are up this week across Arizona. Triple-A Arizona says prices are up over four-cents a gallon from last week to $2.17 a gallon. In Flagstaff, the average price of gas is up nearly four-cents a gallon to $2.31. Some stations are selling gas for $2.23 a gallon and lower. In Prescott, gas prices are up nearly five cents a gallon to $2.20. Some stations are selling gas for $2.09 and lower. Officials say crude oil prices and more people returning to work are a big reason why we are seeing a rise at the pump.