There is "at least one very significant investigative operation underway" at the moment into one of the largest cyber crimes in Canadian history — the CRA phone scam — with both Canadian and Indian authorities working to shut it down, says Public Safety Minister Ralph Goodale.

Goodale made the comments while responding to a months-long CBC Marketplace investigation that traced some of those fake tax calls to illegal call centres in Mumbai.

The CRA scam usually begins with an automated phone message claiming that the target is facing a lawsuit over unpaid taxes owed to Canada Revenue Agency, and demanding they call back or face arrest. Those who return the calls face further threats, before being instructed to pay an outstanding sum, sometimes through bitcoin or gift cards.

While in India, Marketplace spoke to Param Bir Singh, the police commissioner of the Mumbai suburb of Thane, who said he only became aware Canadians were being targeted after he visited the RCMP website and saw a posting about it.

"Nobody contacted us from Canada. It doesn't seem right," he said.

This is going to require, at the international level, an absolutely concerted, focused effort. - Public Safety Minister Ralph Goodale

But Goodale says those conversations are taking place with other law enforcement officials.

"Canadians can be assured that the RCMP treat this very seriously and want to do everything we can — at home and abroad — to shut it down," he said.

Canadian and Indian authorities are not only in contact, but also co-ordinating with other allies and exchanging intelligence, Goodale said.

"This is going to require, at the international level, an absolutely concerted, focused effort — one that involves not just only one country, but a lot of countries putting the pressure on — for the kind of action that is necessary to keep people safe and protect them from this type of activity."

At least 60,000 Canadians have complained about being targeted by the CRA phone scam over the past five years. More than $10 million has been stolen during that same time period, making it one of the largest cyber scams in Canadian history.

'Put a stop to this'

In the days since Marketplace first reported the story, CBC News was flooded with responses via email and social media from Canadians who say they've been harrassed by the threatening calls or fallen victim to the scam, and want the government and police to take action.

"I did phone the RCMP about a year ago and their response was essentially, 'Glad that you know better than to call them back,'" said Manuel Costa. "But [they] weren't interested at all in investigating anything."

"As far as I can tell, the RCMP and CRA think it's our responsibility as individuals to just block these numbers; there's no indication that they're doing anything at all to put a stop to this," wrote Jim Douglas.

"[The] CRA should perhaps be warning potential citizens, and apprise them of what CRA practices are and are not, and also warn them of this scam," said Katie Clough.

Jayesh Dubey is a former employee of one of these illegal call centres in Mumbai, but is now a whistleblower. He said the more money he scammed, the more he took home. (Dave MacIntosh/CBC)

The CRA does have a warning on its website that it won't leave personal information on voicemail, and that its agents do not use "aggressive language" or threaten taxpayers with arrest. When in doubt, the CRA suggests you hang up and either check your account online or call the agency back at 1-800-959-8281.

In the lead-up to last week's story, the RCMP declined repeated requests for an interview or any details about its efforts to combat the CRA scam. Instead, they sent a statement, saying public awareness and education are key.

"Fraud is a global problem without borders," the RCMP said. "By working with various municipal, provincial and national law enforcement and government partners, the RCMP is committed to preventing, detecting and deterring crimes that affect the economic integrity of Canada."

The federal policing agency added that "the best way" to combat these types of crime is through prevention — which is a sentiment Goodale shares.

"If you're being solicited for money over the phone, the chances are that it's a fraud and you should hang up."