U.S. regulators Friday disclosed a broad nationwide investigation into potential oil-market manipulation and said they are expanding surveillance of energy markets, The Wall Street Journal reported Friday.

The Commodity Futures Trading Commission announcement of an ongoing and widening inquiry occurs amid a 4-year rise in crude oil prices in which gasoline, diesel, and heating oil prices hit record highs, Reuters reported Friday.

Oil closed Friday up 73 cents to $127.35 per barrel. Oil has risen about 100% in the past 12 months.

Many Congressional officials and consumer groups have been arguing for a systematic investigation into futures prices, asserting that institutional investors and other speculators have manipulated oil prices and driven them "artificially higher."

Others, including economists and oil executives, argue that the price increases have more to do with the sector's bullish fundamentals, including inadequate crude oil production growth amid rising demand.

Oil Analysis: Strong evidence suggests that the bulk of oil's 4-year bullish run is rooted in fundamentals, with the reduction in the global safety cushion -- the spare oil between daily global oil supply and demand -- accounting for today's near-record oil prices. Still, that's not to say a rigorous inquiry would not yield compelling data or new insights. One area of interest that the inquiry will explore: whether oil storage operators have issued misleading information about oil in their tanks to profit from oil trades, Reuters reported Friday.