Human bone fragments were discovered on a construction site in Calgary. ((CBC))

Workers at a northwest Calgary construction site have found fragments of human bones and police have declared the area a crime scene.

Police were called to the construction site at the 11600 block of 85 Street N.W. on Wednesday afternoon.

"It could be nothing or it could also be a crime scene, so we have to move accordingly," said Calgary police spokesman Kevin Brookwell.

Police don't yet know how long the bones have been at the site, or the sex and age of the deceased, Brookwell said. The construction site, former farmland in the Spy Hill area, is very large, he said.

Officers are working with the medical examiner's office on the case.