Thieves broke into an archaeological site in Edmonton's Mill Creek Ravine over the long weekend and pulled animal bones from the dirt.

Researchers returned to work Tuesday to find the site's protective covers had been peeled back and three bones were missing.

"It robs Alberta of important material culture," said lead archaeologist Haeden Stewart. "It makes it harder for us to do our job in recording all this stuff and getting information we need in order to tell the story of people who used to be here."

Haeden Stewart is the director of the Mill Creek Historical Archaeology Project. (Zoe Todd/CBC)

Stewart launched the site last summer to unearth artifacts from the century-old Vogel's Meat Packing Company and a nearby shantytown.

For the past two months, a team of researchers has scraped back layers of dirt and history, painstakingly recording their progress.

"It's just highly disappointing to see that people don't appreciate and respect the science or the effort or the work that goes into it," said student researcher Joselyn Head.

Head is one of eight MacEwan University students working on the site.

The stolen bones were crucial to her research, she said. Head was curious about bullet casings she found at the site and wanted to check the bones for evidence of gunshots.

"That's usually not how cows in meat-packing plants would have been killed," she said. "I'm pretty disappointed that I didn't get to answer those questions that we had."

Student researcher Josalyne Head scrapes soil from a pit at the Mill Creek Ravine archaeological site. (Zoe Todd/CBC)

Head didn't have time to study the bones before they were stolen and said she likely won't be able to find comparable artifacts before the dig ends.

Stewart and his team are licensed to run the site until the end of August.

Though there was no damage to their equipment, Stewart said the thefts set them back.

"Those things should, in the words of Indiana Jones, belong in a museum," he said.

He suspects the thieves used an open house in July to tour the dig site, before returning at night to steal artifacts.

"In terms of heritage, we're all in this together," Stewart said. "There's a lot out there that needs to be recovered and a lot of stories that can be told.

"It's always better for everyone if we get people who know what they're doing and get those objects to where they're supposed to be."

Stewart recommends that anyone who finds a historical artifact contact Alberta Culture and Toursim.