A 267,000-gallon oil spill, the largest on Alaska's North Slope, reportedly went undetected for up to five days before it was discovered this month.

BP officials told a Tuesday news conference in Anchorage the leak at the Prudhoe Bay oil production complex began as a pinprick-sized hole in a 34-inch pipeline, part of the Trans-Alaska Pipeline System, The New York Times reported Wednesday. The pressure in the pipe expanded the hole to about one-half inch, still small enough so as not to set off alarms.

The spill was detected by a BP worker driving through the area March 2, Maureen Johnson, BP's senior vice president and manager of the company's Prudhoe Bay operation, told reporters.

BP officials said the leak occurred in a section of pipe built during the late 1970's and is the first of such a magnitude resulting from the decay of the aging oil pipeline, The Times reported.

The largest oil spill in Alaska occurred in 1989, when approximately 11 million gallons flowed into Prince William Sound when the Exxon Valdez oil tanker ran aground.

Copyright 2006 by United Press International