A newspaper reports oil company BP was alerted two years ago to problems that caused a major pipeline shut down in Alaska.
Wednesday's Financial Times reports that a BP workers' advocate, Chuck Hamel, wrote about employee concerns in a letter to the chairman of BP's environment committee, Walter Massey. The newspaper says the letter raised concerns about corrosion inside the oil pipeline.
Members of the U.S. Congress have called for hearings to investigate BP's operations at Alaska's Prudhoe Bay oil field.
Democrats on the House Energy and Commerce Committee have said they will examine the shutdown which cut U.S. oil production by about eight percent.
Hearings are set for next month when Congress returns from a recess.