An unlocked case containing two military-grade rifles and two handguns mysteriously arrived in the mail at Bombardier’s shipping department in Toronto last week, CTV News has learned.

Photos obtained by CTV News show that the weapons were marked as property of the U.S. government.

The alarming shipment, delivered by FedEx, contained two Beretta handguns and two M4 rifles, which are used by the American military.

CTV News Public Safety Analyst Chris Lewis said the rifles would be especially dangerous in the wrong hands.

“That firepower is very similar to what we saw used in Vegas,” Lewis said. “Nobody can own them in Canada unless they were owned prior to them becoming prohibited weapons.”

A source told CTV News that the weapons arrived in an unlocked case on Aug. 30 at Bombardier’s shipment department at its Downsview facility in Toronto, just north of Highway 401. There was little paperwork to inform security about what was inside. No ammunition was included in the box.

A receipt indicated that there were two cases in the shipment, but only one arrived at Bombardier. It is unclear what was in the other case, or where it may have been delivered.

The delivery raises serious questions about how four guns were mailed across the border, who sent them and why they arrived at Bombardier.

According to a tracking number on the package, the guns were sent from Spanish Fork, Utah, a city of approximately 38,000 about 135 kilometres south of Salt Lake City, on Aug. 29. They arrived in Memphis, Tenn., sometime after midnight the next day and were processed in Mississauga, Ont., at 7:55 a.m.

The package arrived at Bombardier at 11:34 a.m. on Aug. 30. Bombardier confirmed the delivery in a statement.

"Bombardier confirms that a package was delivered in error to its facility in Downsview. Bombardier's security personnel notified the police as soon as the discovery was made, and the misdirected package was immediately removed from the site," the company told CTV News.

The weapons were turned over to Toronto Police and an investigation is ongoing, police confirmed.

Lewis said it’s unclear how the weapons could have passed through a security check at the border.

“So there’s a total failure of some sort – (it’s) totally illegal to ship them that way,” he said.

“There’s no way on God’s green earth that anybody should be shipping firearms … unless they’re coming through some due process within Canada Border Service Agency’s framework.”

The Canada Border Services Agency said it is looking into the incident and hopes to provide more information by the end of the week.

Federal Public Safety Minister Ralph Goodale did not respond to a request for comment.

FedEx said it is conducting its own “thorough investigation” into the matter and co-operating with authorities.

With a report from CTV News Channel’s Angie Seth

Correction: An earlier version of this story mistakenly referred to the M4 as a fully-automatic rifle.