Gas prices remain on a downward trend coming off the Thanksgiving holiday. Triple-A Arizona says the average price of gas is $2.91 a gallon, which is down a cent from last week. In Flagstaff, gas is down three-and-a-half cents from last week to $2.87 a gallon. Some stations are selling gas for $2.69 and lower. In Prescott, gas prices were down two-cents a gallon from last week to $3.00 a gallon. Some stations are selling gas for $2.85 and lower. Officials say an increase in gas supply has caused gas prices to fall over the past couple of weeks. The drop of prices at the pump is expected to continue for the foreseeable future.