Hamilton Police Service does not own and has not used cellphone surveillance technology in 2015 and 2016, the service told CBC News on Wednesday.

A CBC investigation revealed Calgary, Winnipeg, and Ontario Provincial Police own and use the technology, and at least three other local Canadian police forces have been found to be using it.

But Hamilton's denial it uses the controversial tool is a dramatic change for the service, which has been fighting for nearly a year not to answer a request from CBC Hamilton whether it has or uses the devices.

The technology acts like a cell tower to secretly intercept and track cell phone calls and data in a particular radius. The devices are known as IMSI catchers, cell site simulators, mobile device identifiers (MDIs), and some are known by the brandname Stingray.

The RCMP has used the technology for its own investigations and to assist Toronto and Vancouver police.

Last week the RCMP publicly confirmed for the first time it owns 10 devices but insisted it cannot currently intercept calls, text messages and other private communication.

Civil rights groups across the country have raised concerns about the devices, which, depending on the model, could enable officers to secretly monitor phone calls and anything transmitted from mobile phones, like text messages, photos and location information. Some gather information from the phones of bystanders nearby.

This undated handout photo provided by the U.S. Patent and Trademark Office shows the StingRay II, manufactured by Harris Corporation, of Melbourne, Fla., a cellular site simulator used for surveillance purposes. (U.S. Patent and Trademark Office/Associated Press)

But police who use the tool say they do so with judicial oversight, and that it is an important tool in finding suspects and determining which phones to apply for wiretaps for in serious criminal and national security investigations.

'Not deployed for any Hamilton Police Service investigations'

The Hamilton Police Service has for several months been entangled in a freedom-of-information appeal process over its refusal to confirm or deny whether it has or uses the technology. The police and CBC Hamilton are awaiting a decision from the Information and Privacy Commissioner on the appeal.

But in the meantime, and in response to the CBC revealing the other police forces who use them, Const. Stephen Welton sent the following statement to CBC News Wednesday:

"Hamilton Police have zero [mobile device identifiers]."

"Hamilton Police have no trained technicians."

"An MDI was not deployed for any Hamilton Police Service investigations" (in 2015 and 2016)

Welton later told CBC Hamilton he did not know about the freedom-of-information appeal when he responded to the questions.

IMSI catchers pretend to be a cellphone tower to attract nearby cell signals. When it does it can intercept the unique ID number associated with your phone, the International Mobile Subscriber Identity or IMSI. That number then can be used to track your phone. (CBC)

Another CBC News investigation revealed last week evidence that the devices may be in use near government buildings in Ottawa for the purpose of illegal spying. The RCMP and CSIS are now investigating.

While both the RCMP and Calgary police insist they don't capture the contents of what's shared between devices, policy experts want to know more.

The Office of the Privacy Commissioner of Canada is investigating the RCMP's use of IMSI catchers, following a complaint filed last year.

A spokesperson told CBC the commissioner is looking at what type of information the devices and software can capture.

kelly.bennett@cbc.ca