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The Suncor operation near where officials were seen taking samples from the Athabasca River following a pipeline leak on Monday.Brett Gundlock/ Boreal Collectiv/The Globe and Mail

A leak at a Suncor Energy Inc. oil sands site poured an estimated 350,000 litres of industrial waste water into the Athabasca River over a 10-hour period, causing "a short term, negligible impact on the river" earlier this week, the company said late Wednesday.

Canada's largest oil company provided few details about what chemicals and substances actually flowed into the river north of Fort McMurray, saying in a statement that "our tests confirm the process affected water was a combination of water with suspended solids (clays and fine particulates) and inorganic and organic compounds. It does not contain bitumen."

Suncor spokeswoman Sneh Seetal said she was unable provide further details about the makeup of the industrial waste water.

"It did not contain bitumen but I don't have a further breakdown," Ms. Seetal said.

Earlier this week, Suncor and Alberta's Department of Environment and Sustainable Resource Development disclosed that the company had discovered a rupture on Monday from a pipe carrying industrial waste water used in oil sands extraction and upgrading. The leak at the company's base plant spilled into a pond adjacent to the Athabasca River, and then into the river itself.

Wednesday's statement from company answers one question: how much industrial waste water got into the river. The estimated 350,000 litres that made its way into the Athabasca compares to 2.5-million litres for an Olympic-sized swimming pool.

But Suncor's statement also means the leak went on longer than initial reports suggested. The leak was reported to government officials around 1:45 p.m. on Monday and it was halted at 4 p.m. the same day.

The oil company said that as soon as its staff realized there was a discharge into the river, work began immediately to stop the flow. The company said what it discharged into the river was approximately six parts treated water to one part waste water.

Suncor also said it has hired "a third party" to determine the impact of the industrial waste water entering the river, and Ms. Seetal said water samples continue to be collected.

"Based on the modeling, the current flow of the river, some preliminary volume calculations, we believe there may have had a short term, negligible impact on the river."