Three dogs with a history of violence killed 40 sheep, biting some and frightening others into a stampede that made them pile up and suffocate, Spanish officials said Friday.

The killings — perpetrated by a German shepherd, a Scottish terrier and a mongrel — happened Monday in a pasture in Beunz in northern Navarra region.

Ten other sheep were bitten but survived, the regional government said in a statement.

Witnesses to the attack alerted police and helped them identify the dogs.

Most of the sheep died when the canines chased them toward a sharp rise in the pasture, where they piled up and suffocated, the statement said. Many of the sheep were pregnant.

The witnesses "said the dogs had already been involved in similar acts in the past," the government added. The dogs' owner has been identified but the fate of the dogs was not immediately known.

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