HALIFAX -- The head of Crime Stoppers in Canada says the tip regarding the alleged mall shooting plot in Halifax was likely the most significant ever received in this country for a police investigation.

Ralph Page, president of the Canadian Crime Stoppers Association, said it is an indication of the organization's role in crime prevention.

Police in Halifax have charged two people with conspiracy to commit murder in connection with an alleged plan to carry out an attack at the Halifax Shopping Centre on Valentine's Day. The suspects are due to appear in court on Tuesday to face the allegations against them.

Police had no advance warning of the alleged plans other than an anonymous tip, said RCMP Asst. Commissioner Brian Brennan.

"This investigation started immediately after that single Crime Stoppers tip came in," he told reporters.

Police have said the tip came from within Canada, but have not said anything more specific due to the anonymous nature of the Crime Stoppers system.

"Anonymity is basically what we sell, what people trust. So we protect that at all costs," said Page.

There are more than 100 local Crime Stoppers programs across Canada, said Page, and each is a charity operated by volunteers.

Page said every program guarantees the anonymity of the person submitting the tip, whether by phone or through an encrypted online submission.

Crime Stoppers began in the United States in 1976 to help local police departments solve crimes by receiving anonymous tips.

In Canada, tips submitted through the program have helped lead to more than 190,000 arrests, according to the Canadian Crime Stoppers Association website.

Over time the role of Crime Stoppers has expanded from aiding in crime-solving to also aiding in crime prevention, said Page.

"I think the thing that happened in Halifax is probably the most significant tip that we've ever taken in Canada in terms of our vision of trying to prevent crime," said Page.

"It's kind of a tribute to the Crime Stoppers programs that the awareness level is high enough out in the community for people to think of them and in this particular case save a horrible thing from happening."