Niagara Regional Police evacuated and cordoned off Port Colborne's post office on Thursday following reports of a suspicious package. (QMI Agency)

PORT COLBORNE, Ont. -- Ah, crap.

Port Colborne's post office was evacuated and cordoned off by police Thursday, following discovery of a suspicious package.

The building was closed for several hours as the Niagara Regional Police explosives disposal and canine units swept the facility and examined an envelope that they eventually learned contained, well, crap.

"We suspect it's feces," Const. Derek Watson said. "We don't know for sure, but that's what we suspect it is."

Officials X-rayed the package as police worked to learn about its contents.

There are a number of factors that may deem a package to be suspicious, said Dave Kramer, the Canada Post superintendent for the region.

Though he did not see the actual package in question, Kramer said if a package is found to have no return address, if the wording on it is seen as "odd," or if the item is leaking some sort of fluid, it can be deemed suspicious.