Counterfeit items — from fake Olympic hockey sweaters to bogus passports — as well as drugs such as cocaine and heroin are also arriving in the country through Canada Post, says the criminal intelligence report.
It calls for greater collaboration between police and postal officials to detect suspect parcels, noting legislation limits the ability of police to search and seize mail.
"There is a diverse range of contraband goods being shipped through the Canadian postal system, some of which pose a risk to the safety of Canadians," says the November 2012 report, which draws on information from more than a dozen police forces and Canada's border agency.
Handguns, ammunition, brass knuckles, body armour, hand grenades, stun guns and signal jamming devices are being shipped to Canada from abroad, says the report.
"In one instance, a rocket launcher was even found entering through the mail."
The main entry points for mail shipments of weapons are the cargo facilities at the Toronto and Vancouver international airports.
The Canadian Press obtained a copy of the document under the Access to Information Act, though several sensitive passages were deleted. It was prepared by the RCMP's criminal intelligence section for the organized crime committee of the Canadian Association of Chiefs of Police.
The report helped substantiate what chiefs across the country had been hearing anecdotally, said Bruce Herridge, deputy chief of York Regional Police in Ontario and co-chairman of the committee.
"There's probably more of this going on than we're aware of."
Canada Post delivers more than 10.6 billion parcels and letters to 15 million addresses in Canada each year. International mail flows through large plants in the Vancouver, Toronto and Montreal areas. While Canada Post screens low-risk international mail, other items are referred to Canada Border Services Agency personnel on the premises.
Packages containing dangerous goods pose a risk to postal workers, some of whom have been exposed to substances such as sulphur and acetone, says the report. The Peel Regional Police explosive disposal unit is summoned to the international mail centre west of Toronto an estimated 40 times a year to dispose of dangerous items such as dynamite.
There is an "established trend" of phoney goods being mailed to British Columbia through the postal system, adds the report. "Commonly shipped counterfeit items include clothing, designer handbags, electronics, cosmetics, pharmaceuticals, and also counterfeit currency, passports and identification."
Prior to the 2010 Vancouver Winter Olympics, 14,000 fake NHL and Olympic hockey sweaters were seized at Vancouver's international mail centre.
Seizure data suggests much of the marijuana turning up in the postal system is sent within Canada, while cocaine and heroin arrives from other countries.
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The report also warns that Canada's postal system is "vulnerable to national security threats such as acts of terrorism," as well as mail theft and fraud, and notes that postal workers can be subjected to threats.
"It is suspected that organized crime in Canada is currently involved in the theft of mail."
The report says that because legislation governing Canada Post limits the ability of police to seize mail during the delivery process, police services could pursue agreements with the post office to improve information sharing and investigative processes. Those agencies that have forged relationships with Canada Post — sometimes carrying out joint inspections of mail — "have reported positive outcomes," the report adds.
Herridge said more can be done, particularly since Canada Post is trying to expand parcel traffic as traditional letter mail dwindles.
Additional resources at the post office, regulatory changes and better co-ordination between players could be elements of a stronger strategy, Herridge suggested. "There's going to have to be some discussions around the table to figure out how best to approach this."
While the post office has no comment on the report's findings, "it takes the security and integrity of the postal service very seriously," said Canada Post spokesman John Caines.
"Our team of postal inspectors is responsible for investigating any potential fraudulent or criminal activity related to the postal service and works closely with police from across the country. This approach has worked well, leading to seizures and charges in many cases."
Sgt. Greg Cox, an RCMP spokesman, said the Mounties have "informal but effective" arrangements with the post office and other agencies to ensure the integrity of Canada's mail.
"There are and always will be challenges but we continue to work with Canada Post on these matters."