CALGARY, Alberta (Reuters) - Contaminated water may have spilled into the Athabasca River from a broken pipe at Suncor Energy Inc’s oil sands project in northern Alberta, sparking new fears about pollution of the river from the massive oil sands developments along its banks.

Suncor Energy head office is pictured in Calgary, Alberta June 17, 2009. REUTERS/Todd Korol

The Athabasca is the main source of drinking water for aboriginal and other communities downstream and has been the subject of several controversial reports on its water quality.

The province of Alberta’s environment department said it does not yet know whether the water that spilled from a holding pond contained toxic materials. Samples from the pond are being sent for analysis and it will take at least a day before results are returned. Environment department staff have been at the project site north of Fort McMurray, Alberta, since early on Monday.

Wayne Wood, a spokesman for provincial Environment Minister Diana McQueen, said the volume of water sent into the river has not yet been determined.

“We’re on the ground monitoring the situation,” Wood said. “The pipe got turned off relatively fast.”

Suncor, Canada’s No. 1 oil producer, and other oil sands companies store contaminated water, a byproduct of stripping tar-like bitumen from the sands, in holding ponds. Those ponds became the focus of environmental protests in 2008, when 1,600 ducks died after landing on a tailings pond operated by Syncrude Canada Ltd.

While new regulations introduced after the mass deaths aim to eliminate the toxic ponds, they remain controversial because of the risk of spills into the Athabasca River.

“No one in Alberta should have to be worried about the safety of their drinking supply but that’s exactly the situation we have,” Mike Hudema, a climate and energy campaigner for Greenpeace Canada, said in a statement.

Suncor said the industrial waste water from its oil sands extraction and upgrading operations escaped on Monday morning after a four-inch pipe broke after freezing, spilling the water into a partially frozen outflow pond containing treated water.

However Sneh Seetal, a spokeswoman for the company, said Suncor is not yet certain that any of the water actually flowed into the Athabasca.

“We do not know if this process-affected water was released into the river,” Seetal said. “We are analyzing samples of the pond and the river as part of the investigation.”

Seetal said Suncor’s oil sands project was operating normally despite the spill.

Suncor shares were up 9 Canadian cents at C$30.82 at midday on Tuesday on the Toronto Stock Exchange.

($1=$1.02 Canadian)