CALGARY, Alberta, June 12 (Reuters) - Plains Midstream Canada is not yet able to say what caused one of its pipelines to leak as much as much as 3,000 barrels of oil into an Alberta river last week as it focuses on cleaning up the mess, a company official said on Tuesday.
Plains Midstream, a unit of Plains All American Pipeline LP , said the spill last Thursday in central Alberta has been contained and testing has shown that water downstream meets provincial drinking-water standards.
The company cannot yet say what caused the breach, the second for its Alberta pipelines in just over a year, and does not know if maintenance practices were a factor in the breach of the 46-year-old pipeline.
"Our focus here should be on clean up," Stephen Bart, the company's vice-president, crude oil operations, said at a press conference. "There will be a time to investigate the cause and further discussion ... about maintenance practices can be had at that time."
The spill comes at a crucial time for the energy industry, with operations under the microscope as companies try to advance plans for major trunk lines from Alberta, such as the Keystone XL pipeline to Texas and Northern Gateway pipeline to Canada's Pacific Coast.
Plains estimates that 1,000-3,000 barrels of light, sour crude - oil that has a high sulfur content - leaked from a 12-inch line on its Rangeland south system into a tributary of the Red Deer River, a large waterway that runs cross south-central Alberta.
The company says the oil has been contained by booms on a small portion of a reservoir, where it is being skimmed from the surface. There has been little impact on air quality in the region and only one goose has been found to be contaminated with oil.
Bart said Plains has plugged up the section of pipe that leaked underneath the river and will remove any oil remaining in that portion of the line. The line was not flowing oil when the release occurred.
Last year, much of Plains' 187,000-barrel-a-day Rainbow oil pipeline in northern Alberta was shut down for four months after a rupture spilled 28,000 barrels of crude near a native community in late April. It was one of the largest spills in Alberta in decades.
The company said this month it was putting the final touches on reclamation efforts.