COLVILLE, Wash. (AP) — The Washington state Department of Fish and Wildlife says toxicology reports show six wolves found dead this year in the state’s northeast region were poisoned.

Fish and Wildlife officials said Monday the agency has been investigating wolf deaths within the Wedge pack territory in Stevens County since local authorities discovered four dead wolves on Feb. 18.

The agency found two additional wolves in the following month.

Officials say toxicology results revealed all six died from ingesting poison.

Anyone with relevant information is asked to report it confidentially by calling Fish and Wildlife’s poaching hotline. Conservation groups are offering a $51,000 reward for tips leading to convictions.