The family of Canadian billionaire Barry Sherman has closed its private investigation into the murder of the pharmaceutical magnate and his wife Honey, two years after they were found strangled in their Toronto home.

The decision to wrap the inquiry has ignited fresh speculation about a case that has transfixed Canada.

Canadian officials originally believed the deaths had been a murder-suicide before private investigators hired by the Sherman family concluded it had been a double murder.

A more than $7.5 million reward offered by the family for information leading to an arrest and conviction remains unclaimed.

“When you offer a 10m [Canadian dollars] reward and nothing has happened, you can see that the people who are involved either don’t need the money or fear that if they come up with the answer, they’ll be eliminated,” Murray Rubin, a longtime friend and business associate of Barry Sherman told The Sunday Times of London.

Barry Sherman, who founded Canadian pharmaceutical giant Apotex, was estimated to be worth nearly $4 billion at the time of his death, but had faced financial woes in his final years.

A month before the murders, work was stalled on a home for which the Shermans had just obtained building permits.

Their charitable giving had also fallen off sharply in recent years.

The billionaire was known in the country for being extraordinarily litigious and at the time of his death was involved more than 150 lawsuits.

There were enemies too, so many that Barry was known for indulging in black humor about being assassinated by one of them.