UPDATE 1-Suncor releases water from oil sands pond into Athabasca River

* Volume and toxicity of release not yet known

* Company has not been asked to shut down operations

* Shares up 0.4 pct (Adds details)

CALGARY, Alberta, March 26 (Reuters) - Suncor Energy Inc , Canada's No. 1 oil producer, released water from a holding pond at its oil sands project into the Athabasca River, Alberta's environment department said on Tuesday.

Alberta Environment said it does not yet know whether the water that was sent by pipe into the river 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.

The company, which could not be immediately reached for comment, has not been asked to shut down any of its operations because of the spill, Wood said.

Suncor and other oil sands producers 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.

Suncor shares were up 13 Canadian cents at C$30.86 at midmorning on the Toronto Stock Exchange.

($1=$1.02 Canadian)

(Reporting by Scott Haggett; Editing by Gerald E. McCormick and Peter Galloway)

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Keywords: SUNCOR OILSANDS/SPILL