Crews in Alaska have finally capped an oil leak this past weekend caused by a local resident who fired a gunshot into part of the Trans-Alaska Pipeline which spilled about 300,000 gallons of crude into a small forested area.

Although authorities called the Thursday incident an apparent isolated act of vandalism, both environmental and industry critics say it highlights the line's vulnerability to sabotage and attack. The Alaska pipeline runs through remote wilderness and carries about a fifth of U.S. domestic oil. The critics, including some pipeline workers, have long complained of chronic maintenance and repair problems, which they say could result in a catastrophic spill.

Law enforcement officials said they had no immediate motive for the Thursday afternoon shooting, but have ruled out terrorism. They said the man arrested in the incident, identified as 37-year-old Daniel Carson Lewis, was intoxicated and with his brother when he fired a shot piercing the half-inch steel pipeline in a remote area north of Fairbanks. He was charged with felony assault and criminal mischief, and ordered held in the Fairbanks Correctional Center on a $1.5 million bond. Mr. Lewis hasn't entered a plea pending a hearing.

The spill was detected in a routine overflight by security officials of the Alyeska Pipeline Service Co., Anchorage, Alaska, which operates the pipeline and is owned by a consortium that includes Exxon Mobil Corp., Irving, Texas, Phillips Petrolem Co., Bartlesville, Okla., and London's BP PLC. Alyeska said this is the largest spill on the 800-mile pipeline since another vandalism incident in 1978 that resulted in a 700,000 gallon spill. No one was arrested in that case.

Officials say there have been more than 50 documented cases of people shooting the line during the pipeline's 24-year history, both intentionally and by accident. This is the first time a bullet actually punctured the line, renewing concerns among environmentalists and others over the pipeline's vulnerability.

"It's pretty darn tough to guard the whole thing at once," said Ross Coen, executive director of the Alaska Forum for Environmental Responsibility, a Fairbanks environmental group.

Alyeska officials said they moved quickly to staunch the leak. As equipment was brought in to patch it, the entire pipeline was shut down and tankers in the port of Valdez loaded stockpiled crude oil.

Still, critics say, it took the company until Sunday to stop the leak.

"For them to not be able to cap that small of a hole quickly is preposterous," said Chuck Hamel, a former oil and tanker broker in Alexandria, Va. who has been a frequent Alyeska critic.

An Alyeska spokesman said the company moved as fast as it could. Meanwhile, Alyeska is still investigating why smaller spills of between 200 gallons and 2,200 gallons broke out at three of its pumping stations after the pipeline was restarted following a scheduled maintenance shutdown last month.

Although the oil didn't escape the facilities, pipeline critics say the spills underscore their concern the pipeline is beginning to show its age. Complaints by pipeline whistle-blowers have included concerns about faulty and corroding equipment. Alyeska officials in the past acknowledged some of the problems and have said they responded to many of the concerns.

Write to Jim Carlton.