SEATTLE, (AP) -An engineering firm raised a red flag more than four years ago about BP PLC’s monitoring of its Alaska oil pipelines, documents show.

The draft report by Seattle’s Coffman Engineers, published in November 2001, is among documents being reviewed by a federal grand jury in Anchorage that is investigating a March oil spill of more than 200,000 gallons from a pipe on the western side of the Prudhoe Bay oil field.

BP shut down part of its operations at the oil field this month after leaks and corrosion in low-pressure pipe were found on the eastern side.

The engineering firm’s final report was significantly toned down after BP responded to the draft, the documents showed.

The grand jury is looking into possible criminal violations of the federal Clean Water Act, which carries penalties for negligent conduct that leads to an oil spill.

Coffman also has cited corrosion problems as the cause of small leaks and other damage that triggered the partial shutdown this month.

The Coffman documents were made public Friday on the Project on Government Oversight Web site by Charles Hamel, a former oil broker and a watchdog of Alaska’s oil industry. In a letter sent Aug. 22 to the federal Office of Pipeline Safety, Hamel accused BP of “whitewashing” away criticism.

Coffman’s work was done under contract with the state of Alaska, which requires the monitoring effort.

The 2001 report questioned whether BP was using remote-operated devices that check for corrosion and other wear extensively enough. Most of the comments about the devices were eliminated from the final report, published early in 2002.

In the aftermath of last March’s spill, BP acknowledged that the transit lines in western Prudhoe Bay had gone without an inspection by the remote-operated device since 1998, and it has been scrambling to make those inspections.