The final 11 people still facing charges in relation to a police operation targeting alleged Montreal Mafia members have had their charges stayed.

A judge approved the request Monday, which came from the Crown.

The accused were arrested as part of Operation Clemenza, a multi-pronged operation that led to the arrests of close to 50 people on charges ranging from drug trafficking to kidnapping to firearm possession.

There had been speculation that prosecutors were uneasy about divulging the details behind a secretive and controversial surveillance technique used during the investigation.

During the police investigation between 2010 and 2012, RCMP officers intercepted close to one million PIN-to-PIN BlackBerry using a new technology. At the time of the first arrests in 2014, police boasted about the new method.

The defence asked for more information about how police gathered evidence. That request prompted the Crown's request to have the charges stayed.

"A careful study was done of those questions with team prosecutors and the police as well as, in this case, the RCMP," said Crown prosecutor André Albert Morin. "We couldn't answer those questions, so we could not meet our disclosure obligations to the full extent."

Walid Hijazi, a criminal defence attorney, questions whether new surveillance techniques will hold up in court.

"I understand that the police do not want to disclose secret elements around this technology because there are ongoing investigations...So to not jeopardize these investigations and to not put public safety at risk, they decided to keep the technology secret by dropping the charges."

Earlier this year, the Crown stayed charges against 36 people also arrested as part of Operation Clemenza, but the reasons why were unclear.

With files from Ryan Hicks