U.S. authorities are investigating whether British oil giant BP manipulated U.S. oil and gasoline markets.

BP officials have confirmed the investigations, first reported Tuesday in The Wall Street Journal.

The newspaper reports that BP faces two separate investigations. The first is focused on possible manipulation of global over-the-counter crude oil market prices in 2003 and 2004. In the second inquiry, investigators are examining a single day of trading on the New York Mercantile Exchange in 2002.

BP had already been under investigation by U.S. officials. The company has been summoned before Congress next week over problems at its Alaska pipelines. The company's executive officer, John Browne, was recently summoned to testify in Texas in connection with a refinery explosion in 2005 that killed 15 people there.

Commodities regulators also have alleged BP manipulated the U.S. propane market in early 2004.

Some information for this report was provided by Reuters.