CHICAGO (CBS) – Pain at the pump continues in Illinois, as the Great Lake states wrestle with the some of the highest gas prices in the country.

“Every area in the Great Lakes is on the most expensive list,” said Patrick DeHaan, senior petroleum analyst for GasBuddy.com.

WBBM Newsradio’s Lisa Fielding reports Illinois is at the top of that list, at an average price of $4.09 per gallon. The biggest factor in the recent spike in prices was a pipeline spill in Wisconsin, which prompted a shutdown of supplies to the Chicago area.

“Illinois is now the leader in the lower 48 [states] for the highest gas price average. Chicago prices are nearing levels that we haven’t seen since May and April,” DeHaan said.

LISTEN: WBBM Newsradio’s Lisa Fielding Reports

Prices peaked over the weekend, and are still significantly higher than last week. It appears that prices have begun dropping, at least a bit.

“Prices in Chicago are actually down about 9 tenths of a penny since midnight, so the worst is likely behind us, but prices remain about 30 cents higher than where they were just a week ago,” he said.

According to DeHaan, it might be a while before gas prices in Illinois dip back below $4 per gallon, given the refinery problems in the Midwest.

“Three refineries in the area – two in the Chicagoland area, one down towards St. Louis in Wood River, Illinois – all virtually suffering issues at the same time,” DeHaan said.

However, fire at Chevron Corp.’s refinery in Richmond, Calif., should not have any impact on gas prices in Illinois.