Operators temporarily shut down the new $5.2 billion Keystone oil pipeline that runs through the St. Louis area after a large leak was reported in North Dakota.

Witnesses on Saturday morning reported seeing a six-story geyser of oil gushing from a pump station in Sargent County in the southeastern part of the state.

Officials with TransCanada, the pipeline's owner, blamed a bad fitting and shut down the line until all such fittings could be examined. They expect the system to be down a few more days.

Company officials estimated about 21,000 gallons leaked. A berm around the station contained most of the spill. Some contaminated soil is being removed.

"What's important to recognize here is that in nine minutes, we had valves remotely closed on either side of the pump station, stopping the flow of oil to the site," company spokesman Terry Cunha said in an email. "This demonstrates TransCanada's pipeline safety systems are working."

The Keystone pipeline stretches 2,151 miles from Alberta's Athabasca tar sands to the ConocoPhillips' Wood River refinery in Roxana, then on to Patoka, Ill. One of the longest and most expensive pipelines ever built in North America, Keystone can carry almost 600,000 barrels a day, enough to supply about 2 percent of the country's daily demand. Oil began reaching the refinery in late June.

The pipeline has been the target of environmentalists, landowners and others who question its safety.

The leak Saturday was the 12th reported at a Keystone pipeline pump station, but most were less than 20 gallons. In January, a pump seal failed and leaked about 10 gallons at a pump station in Clinton County, Mo., the only leak that has occurred in Missouri. No spills have been reported in Illinois.

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EDITOR'S NOTE: Earlier versions of this story contained an incorrect figure for the Keystone pipeline's capacity. This version has been corrected.