Six Pacific state senators are asking the Justice Department to investigate whether oil refineries manipulated the price of gasoline when it hit near-record prices in the region from May through October.

The price was more than $4 a gallon during that period and broke the $5 mark last month in California, even though the price of crude oil has been declining.

Analysts have said the near-record prices were the result of refinery problems. But the senators point to a review of California refinery emissions data showing inconsistencies between the time refineries were producing petroleum products and when maintenance shutdowns were publicly reported.

They said misleading reports of shutdowns could have created a perceived shortage of gasoline.