The Canadian military mobilized search aircraft in a desperate hunt for a large passenger plane they believed had crashed in Nova Scotia's Annapolis Valley, after a farm market inexplicably emitted an electronic SOS signal, CBC News has learned.

It was a fruitless search.

According to Transport Canada's Civil Aviation Daily Occurrence Reporting System, the Avery's Farm Market in Berwick started sending out a signal on the night of Nov. 14, telling rescue authorities a British Airways Boeing 777 passenger liner with hundreds of people aboard had crashed.

A Cormorant helicopter was launched, an Aurora aircraft was diverted and another one was put on standby as members of the Civil Air Search and Rescue Association were tasked to search for the plane.

"I guess the signal was a distress signal about an airplane that had crashed in this location, but there was actually no airplane that crashed," said April Huntley, a supervisor at Avery's Farm Market.

The plane in question, meanwhile, had arrived safely in Atlanta after taking off from London's Heathrow Airport several hours earlier.

Huntley said that the next day, government officials came to the store to scan the building to find the source of the emergency signal.

It turned out to be a digital video camera and recorder — the security system at Avery's. Then the mystery deepened: shutting off the security system did not shut off the signal.

"They did tell us that they had airplanes and stuff, they had sent out search teams and everything because they actually thought there was a crash," said Huntley.

"We're not really sure why the signal was coming from the security system."

Emergency signal leads to search

The store's security system had been in place for years, Huntley said, and it's still unclear how a vegetable store could mimic a crashed airliner.

The Canadian Forces confirmed the futile search to CBC News but did not provide an explanation.

"An ELT [Emergency Locator Transmitter] signal was reported, prompting JRCC Halifax to task an airborne Aurora aircraft, a Cormorant helicopter and an additional Aurora aircraft that was later stood down prior to departure," Maj. R. Martell Thompson, a spokesman for Joint Task Force Atlantic, said in a statement.

"The signal was later determined to be emitting from the Berwick area, and was referred to Industry Canada and CASARA for further investigation."