WISCASSET (AP) - Police believe dogs are responsible for an attack that killed more than a dozen sheep over the weekend.

Investigators say the dogs either jumped or knocked down an electric fence to get at the sheep. Farmer Lee Straw discovered the carnage after getting a call about his sheep being loose at 5:30 a.m. Sunday.

Bob Horne, who owns the land where the sheep were set out to pasture, said he was shocked when he saw the dead sheep. "It's thousands of dollars worth of a farmer's livelihood," he said.

Police, along with Straw and Horne, believe dogs, not coyotes, were responsible because only a few of the 15 dead sheep were eaten. "It has to be dogs, and more than one, because one wouldn't do that much damage," said officer Kathy S. Williams of the Wiscasset Police Department.

Williams said the dogs probably toppled the fence, which delivers an electric shock on contact, to enter the pasture. She said the sheep were valued at around $2,000.

Because about two-thirds of those killed were intended for birthing lambs, they would have been worth $10,000 over the course of several years, Straw said.

The attacks were the worst for Straw in three years. He said he lost 17 sheep in 2004 to a group of dogs that police never found.