Police have appealed for information and issued a warning to the public after 25 sheep were found dead in this morning.
The illegally slaughtered sheep were found at about 8am in a field off Welford Road at a farm in the Thornby area, near Naseby off the A14.
Inspector Tracy Moore, who leads rural crime investigations for Northamptonshire Police, said: "Unsurprisingly, the owner of these sheep is devastated and my officers are working round the clock to bring whoever is responsible for these monstrous acts to justice."
The incident is being investigated by Operation Stock, the ongoing probe into acts of sheep butchery and theft.
This is the 12th report of illegal sheep slaughter in Northamptonshire since February.
There has been eight reports of sheep theft and in July there was also a report of a lamb tied up with electric fencing in the Moulton area.
In total, 118 sheep had been killed in the 11 crimes recorded before this latest incident in Thornby.
Insp Moore said: "I am appealing for the public to be extra vigilant and to keep an eye out for suspicious activity in rural areas or around livestock – it is likely offenders are carrying out daytime scoping exercises and I urge people who see suspicious vehicles to contact police.
"I also appeal for anybody who has any information about the sale of cheap meat with unknown provenance to come forward – we remain concerned about illegal meat entering the human food chain, as recent use of veterinary medication could mean it’s unfit for human consumption."
Consumers should avoid buying meat cheaply in suspicious circumstances and try to buy from reputable outlets.
Anybody with information should contact police on 101 quoting incident number 89 of Monday, September 9.
Call 999 if you believe a crime is occurring.