Police investigators, who were called to the party offices at 11:20 a.m. to examine a suspicious package that appeared stained with blood, said the grisly delivery was made via Canada Post, the Canadian Broadcasting Corp. reported.
Members of the Hazmat Unit and Emergency Operations Section were brought in to inspect the package. The determination that it was a foot also meant major crimes investigators had taken over the case because the arrival of the foot means "there's a body without one," city police Staff Sgt. Bruce Pirt told the news network.
Efforts were under way to track the package's origin.
The CBC said the Royal Canadian Mounted Police and Montreal Police were investigating the discovery of a human torso in a pile of garbage in the city to determine if it was related to the foot in Ottawa.
Conservative Party spokesman Fred DeLorey referred questions to Ottawa police.
The incident rattled some government officials in Ottawa.
"It's shocking for somebody to do that," Labor Minister Lisa Raitt said. "I'd hate to be the one opening that."