Six people have been charged in connection with a $5-billion money-laundering and fraud case being investigated in Toronto and the U.S.

Toronto police began their investigation with a "romance scam" reported in the city in August, 2014. A 63-year-old Toronto widow had been defrauded of $609,000, police said at a news conference on the fraud case Thursday.

During the investigation, Toronto police discovered the case had connections to a larger operation that was under investigation by the U.S. Postal Inspection Service and the Federal Bureau of Investigation (FBI).

The forces worked together to uncover the identities of those alleged to be involved in the cross-border laundering and fraud investigation. Police said conspirators allegedly attempted to defraud victims of more than $5 billion.

Authorities allege that proceeds were obtained by a variety of scams, like the Toronto romance scam, directed at random members of the public.

Victims were encouraged to wire funds to various bank accounts. The money was then laundered and circulated to those directing the schemes, police said.

Earlier this month, two people were arrested and charged in connection with the initial romance scam.

Lineo Molefe, 31, of Toronto was charged with laundering the proceeds of crime and fraud over $5,000.

Ikechukwu Amadi, 34, of Mississauga faces the same charges in the romance scam, but was also charged by the FBI in connection to the larger, $6.5-billion wire fraud and laundering case.

Amadi also goes by the names Martin Acker and Martins Acker Jr., police said. He is alleged to have claimed to be a representative of the United Nations, and police said he was using forged UN identification dating back as far as 2011.

Police said 41-year-old Akohomen Ighedoise, also of Toronto, was also charged in the $6.5-billion laundering investigation.

Ighedoise is alleged to be a member of an organization called "The Black Axe" or "Neo-Black Movement of Africa," which has ties to cities around the world. Officials said he was involved in laundering the proceeds of crime with other members of the group.

He has been charged with laundering the proceeds of crime, fraud over $5,000 and participating in a criminal organization.

"It's come to our attention that persons who have identified themselves with The Black Axe organization in Toronto are attempting to exert influence in the community here, particularly in the ex-patriot Nigerian community," Det. Sgt. Ian Nichol said Thursday.

The U.S. intends to seek extradition of both men when the Canadian cases have been concluded, police said.

Officers believe there may be more victims, and ask anyone with more information to come forward. They're asked to contact Det. Const. Mike Kelly at 416-808-7824, or Crime Stoppers anonymously at 416-222-8477 (TIPS).