The Alberta government says more study is needed on the effects of oil sands development on the environment.
Research from a government-appointed panel has failed to resolve differences between what official estimates say and the conclusions of independent scientists.
The panel says studies by the two sides aren't comparable because they were designed to measure different things.
Alberta has long said that contamination in the Athabasca River comes from natural sources.
But University of Alberta researchers say they have traced hydrocarbons and heavy metals directly to the oil sands.
The government has been backing off its position ever since its monitoring approach was heavily criticized by several academic groups.