Scores of horses confiscated from travellers by police have been stolen from the secret location in Northumberland where they were being held.
Detectives believe travellers raided the site, near Heddon-on-the-Wall, near Throckley, to recover their animals, which were impounded after being allowed to roam free.
The raid is a major embarrassment for police chiefs who hailed last week’s opADVERTISEMENTeration - the biggest of its kind ever mounted in the UK - as a major success.
More than 50 Durham police rounded up 40 horses and 20 sheep in Hunwick, near Bishop Auckland.
Operation Beausaddle was the force’s response to a surge in complaints about stray horses causing havoc on the busy A689 into Bishop Auckland.
The animals were moved 30 miles away to what was supposed to be a secret location.
But on Saturday night, only 48 hours after the police raid, a fleet of trailers was seen arriving at the site.
Police said the raiders cut through a fence to reach the animals, before leading them over two fields and a ditch to horse boxes parked by the A69.
During the raid, one of the horses suffered a broken leg and had to be put down by police.
No-one has been arrested for theft in connection with the incident and Durham Police are still searching for the horses.