A gasoline tanker truck fills up with gas at a distribution center Friday in Brisbane, Calif. Retail gas prices jumped a cent Friday to a new national average over .96 a gallon, putting them on a course to hit by early next week. Oil futures, meanwhile, traded in a narrow range as investors tried to determine whether recent price declines were temporary.

New York ? Oil prices fell sharply Thursday after the Energy Department reported unexpected declines in crude oil and gasoline supplies last week, but said the drop in crude inventories was due to temporary delays in unloading oil tankers along the Gulf Coast. A stronger dollar and concerns about gas demand also weighed on prices.

Retail gas prices, meanwhile, rose to a new record above $3.95 a gallon.

Light, sweet crude for July delivery fell $4.23 to $126.80 a barrel on the New York Mercantile Exchange, their lowest level since early last week. Prices were more than $2 lower in morning trading before the EIA report was issued, but shot up by more than $2 a barrel immediately after the report’s release before turning lower again.

In Washington, meanwhile, the Commodity Futures Trading Commission revealed that it is six months into a wide-ranging investigation of U.S. oil markets, with a focus on possible price manipulation.

The CFTC said it started the probe in December and was publicizing the investigation “because of today’s unprecedented market conditions.”

The market’s initial ambivalent reaction to Thursday’s inventory report partly reflects a deeper battle between investors who believe prices have risen far beyond levels that can be justified by underlying supply and demand fundamentals, and those who believe speculative money will continue flowing into oil futures, sending prices higher regardless of the market’s fundamentals.