Four national animal welfare groups have added a total of $17,500 to the reward for tracking down whoever killed 25 cats in a New York suburb.

Rewards of $5,000 each were announced Tuesday by the Animal Legal Defense Fund, People for the Ethical Treatment of Animals and the Humane Society of the United States. The Defense of Animals Fund added $2,500.

The organization Alley Cat Allies had previously posted a $750 reward.

The cats were found Thursday in plastic bags hanging from trees in Yonkers. Tests on three bodies showed they had been killed with blows to the head. Some cats had been dead about a year, some just three days.

There had been no arrests as of Tuesday afternoon. The Westchester County SPCA expressed gratitude for the reward offers.