Queensland police are investigating the theft of about 5,500 Dorper sheep from a western Queensland farm. The sheep are valued at more than $1.7 million. This was reported by Qazaqyia.kz citing The Guardian.

Police said the sheep were stolen from a property outside Blackall, about 830km west of Brisbane, between February and May this year.

Detective Sen Sgt Paul Elliot, from the rural and stock crime squad, said the sheep had an estimated value of about $1.7m (£899,000).

The stolen sheep are fitted with white National Livestock Identification System tags and are Dorper sheep, a breed with white wool but a black face. Both ewes and rams were taken.

Elliot urged anyone with information about the theft or who had seen Dorper sheep matching the description in the area to come forward.

"Livestock theft investigations can be complex, often spanning large geographical areas, which is why we work closely with producers, saleyards, transport operators and industry stakeholders to identify offenders and disrupt criminal activity," he said.

The AgForce general president, Shane McCarthy, said it was a "a concerning amount of sheep that have been stolen" and would have a significant effect on the farm's bottom line.

"We're seeing a concerning rise in the number of incidents like this happening across the state," he said. "We would trust that the police are taking these matters very, very seriously."

He said a sheep theft of that scale would require a plan, time and more than one person. Sheep rustlers will sometimes take a group into a property where they can be bred to gain the value of their progeny and then slowly sold to abattoirs over time.

Thefts are often discovered at the abattoir, he said.

"I would say that it's been thought out for a while," he said. "I would suggest that one or two sheep here and there, even up to you know 10 or so sheep, is opportunistic. When we're talking these numbers, they're organised."

It is not yet clear how the sheep were stolen, such as being loaded on to several trucks or mustered.

Dorpers are bred to be eaten, not for wool.

The Blackall-Tambo mayor, Andrew Martin, said the herd was probably not all taken in one night.

"I'm suspecting a number of smaller hits and sneaking them off to the abattoir or whatever it is they're doing with them," he said.

Farms in some parts of Queensland can rival the size of some countries. Stock theft is typically discovered during a muster.

Martin, who has farmed Dorper sheep, said some properties have as many as 25,000 sheep. It is possible to lose thousands by them escaping, from an animal attack or just miscounting them, without noticing for a long period of time, he said.

"This is an age-old problem. Potty dodging is a bit of an art, and it's been going on ever since potties were there to be dodged," he said, using Australian slang for stock theft.