INDIANAPOLIS - Gas prices that jumped to $3.99 a gallon or higher in central Indiana over the weekend are among the highest in the U.S.
AAA's Fuel Gauge Report indicated that Indiana's average for a gallon of regular unleaded is $3.95, with prices in Indianapolis slightly higher than that.
In the Indianapolis area, prices are up nearly 30 cents a gallon in a week, and the current price is nearly 50 cents a gallon higher than this time a year ago.
Nationally, Indiana ranks seventh-highest in gas prices, behind Hawaii, Michigan, Alaska, Illinois, North Dakota and California, AAA said.
South Carolina has the nation's lowest gas prices, at $3.20 a gallon. The national average is $3.62 a gallon.
Prices have exceeded $4 a gallon at some stations in the Indianapolis area, primarily north of the city.
The increases appear to have been sparked by rumors of a refinery issue in the Chicago area, mentioned in a blog post on GasBuddy.com , which tracks real-time gas prices nationwide.
"This is due to trade rumors of a refinery 'caught' buying gasoline from other refineries," read the post from Patrick DeHaan, of GasBuddy. "Typically this happens when a refinery suffers from an unexpected glitch resulting in lower gasoline production. The affected refinery is then forced to buy gasoline on the market to cover its previous contractual obligations."
DeHaan said the rumor "has a tendency to spook the market, especially amidst an already tight supply of gasoline."
DeHaan accurately predicted the weekend price increase and said it's possible prices in Indiana could go higher than current levels.