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LAKEWOOD, Colo. — It was a mystery for people who live and work around a retention pond in Lakewood.

Something killed off or injured dozens of geese and ducks at the small pond at 3222 S. Vance St. starting in January.

Now, the U.S. Fish and Wildlife Service needs help identifying the culprits.

“They spend their life on water. They are entirely dependent upon it,” said Ryan Moehring with U.S. Fish and Wildlife Service.

But this source of life ended up taking the lives of 33 ducks and geese that depend on it. It injured eight others.

“It’s unclear why anyone would introduce a substance in a waterway like this. It’s illegal to do so and obviously harmful to wildlife,” Moehring said.

Someone poisoned the retention pond, repeatedly over three weeks, starting around Jan. 18.

A picture from the USFWS shows a suspicious white sheen on the water, along with a duck covered in it.

“We sent a number of samples to the National Wildlife Health Center. Those analysis show that the contaminant introduced to the waterway was a commercial grade cooking oil,” Moehring said.

Investigators believe it came from nearby upstream, from a strip mall with several restaurants in it. The owner of Spicy Mexican Grill recycles his cooking oil.

Arturo Gonzalez said dumping it would be more trouble for anyone than it’s worth.

“I don’t believe someone would throw away the oil up there. After we use it for eight days, we have a place to put it in,” he said about his restaurant’s used oil receptacle near his dumpster.

Federal investigators said this protected wildlife can’t duck the dangers of cooking oil which damages their feathers’ ability to insulate them from the cold, so they freeze.

“If somebody did it, put them in the jail. Ducks, fish or whatever, they don’t deserve that,” Gonzalez said.

It is foul play that harms the very creatures who typify healthy land and water.

“It’s extremely sad to witness animals suffering. The silver lining is we do have law enforcement folks and conservation groups whose job is to protect them,” Moehring said.

Anyone with information is asked to call authorities at 720-981-2777, ext. 226. The contamination carries a fine of up to $15,000 for each occurrence — of which there are multiple in this case.