Intelligence experts are scratching their heads over the publication of detailed floor plans for the secret eavesdropping station on Leitrim Road.
Diagrams of Canadian Forces Station Leitrim appeared online Wednesday but were removed Friday.
The plans were posted in a Public Works tender for renovations to the base's operations room.
Canadian Forces Station Leitrim has long been a listening post for the Communications Security Establishment Canada. It's a high-security facility used to intercept foreign and domestic radio signals.
"Quite frankly I was startled to see the diagrams there, and the degree to which the detail was there," said Tom Quiggin, who worked in military operations centres for 20 years and specializes in intelligence work.
"If you layer the information that's there, which is to say, look at the actual diagram of the ops centre itself — and it shows the number of chairs, the number of people, the positions they work at, et cetera — and then layer that over the wiring diagram, the heating, ventilation, air conditioning and everything else, you can get a pretty good idea of what all is in there, how many people work there and how the workflow and procedures would go through."
Construction plans in high-security buildings are often housed somewhere on site where contractors can view them, but not take photographs of or copy them, Quiggin said.
"In this case I'm not sure where the breach occurred, but whoever would have put it up into the open source has clearly made an error," said Wayne Boone, a retired military police officer who specializes in infrastructure protection.
"What concerns me most is the indications of what might be going on in some of the interior rooms within the building that could focus an adversary in terms of surveillance."
The Department of National Defence did not respond to requests for comment.