Swindling customers is an ancient art, at least according to recent findings by British scientists.

Scientists from the University of Manchester revealed that a third of the ancient Egyptian animal mummies they had scanned had actually been empty, with no remains inside them.

They also revealed that only a third of the mummies scanned contained complete animals, while another third of the mummies scanned contained partial animal remains.

The rest of the mummies contained “organic material such as mud, sticks and reeds, that would have been lying around the embalmers workshops, and also things like eggshells and feathers, which were associated with the animals, but aren't the animals themselves,” said Dr. Lidija McKnight, an Egyptologist from the University of Manchester who led the research team.

The research team has been conducting the largest scanning project of its kind at Manchester Museum and the University of Manchester; they have analyzed more than 800 animal mummies so far using X-rays and CT scans.

While Ancient Egypt is famously known for its human mummies, the mummification of animals was not only prominent, it was the source of big business, as animal mummies were sold to be used as votive offerings to the gods. The dead animals played an important role in the religious lives of ancient Egyptians.

These mummies “were of tremendous importance in Egyptian culture,” McKnight told The Washington Post .. “You’d get one of these mummies and you’d ask it to take a message on your behalf to the gods and then wait for the gods to do something in return. That’s kind of their place in the religious belief system of ancient Egypt, and that’s why we think there were so many of them."

This national animal mummification need created a massive industry that is believed to have lasted more than a thousand years, with scientists estimating that up to 70 million animals were mummified and buried in underground catacombs at more than 30 sites across Egypt. The researchers believe this industry spawned a breeding program to accommodate the large numbers of animals that were killed. However, this bustling industry still found it difficult to keep up with the great demand, as evidenced by the mummy fakes that were recently found.

The Telegraph reported that archaeologists have found evidence of ancient customer dissatisfaction inside the necropolis of Saqqara, where Egyptologists reportedly discovered potsherds that seemed to detail the jailing of six mummy makers and calling for "one god in one vessel."

On the other hand, Dr McKnight doesn’t think the empty mummies were a scam. She said that they shouldn’t be viewed as fakery and that there was probably a “much more innocent explanation for what was going on.”

According to the BBC, the researchers think the pilgrims may have known the mummies were empty. Dr. McNight said Egyptians still considered them special due to their proximity to the animals.

"So we don't think it’s forgery or fakery. It's just that they were using everything they could find. And often the most beautifully wrapped mummies don't contain the animal remains themselves."

So were the Ancient Egyptian mummy dealers just offering different types of mummies to their loyal customers? Or were they natural con-artists? We may never know.