TORONTO -- The family of a billionaire philanthropist couple found dead earlier this month has hired a team of former homicide detectives to investigate the deaths deemed "suspicious' by police, a lawyer for the family said Thursday.

Brian Greenspan said the private investigators were hired "to provide a second lens and to ensure that no stone is left unturned."

Barry Sherman, 75, and his wife, Honey, 70, were found dead in their Toronto mansion on Dec. 15.

Police have said both died of "ligature neck compression," but have released few other details about the investigation, which is being led by homicide detectives.

Investigators are still poring over the couple's home, but a police spokesman said there are no updates at this point.

Among the private investigators hired by the family is Tom Klatt, a former homicide investigator with the Toronto police, said Greenspan.

Klatt has worked on more than 70 murder investigations, according to the website of his firm, Klatt Investigations.

His services have been retained by "many of Canada's wealthiest families who were in the process of dealing with life altering family issues," says his website.

Some media reports have said police were initially leaning toward a murder-suicide theory, which the Sherman family has strongly rejected.

Toronto Mayor John Tory said Thursday the Sherman family has expressed concerns about the police communications with the media during the ongoing investigation.

Tory, a member of the Toronto Police Services Board that oversees the force, has shared those concerns with the police, said the mayor's spokesman, Don Peat.

"He (Tory) conveyed those concerns dispassionately and did not make any requests of police, but simply relayed their concerns about communication of information, similar to what he would do when other families he contacts have concerns with police or anyone else," said Peat.

Thousands of people, including Prime Minister Justin Trudeau and Ontario Premier Kathleen Wynne, attended a memorial service for the couple last week.

Barry Sherman founded Toronto-based Apotex Inc. in 1974 with two employees and gradually turned it into a generic drug giant. Along the way he amassed a vast fortune, recently estimated by Canadian Business magazine at $4.77 billion, making him the 15th richest person in Canada.

Honey Sherman was a member of the board of the Baycrest Foundation and the York University Foundation. She also served on the boards of Mount Sinai's Women's Auxiliary, the Simon Wiesenthal Center and the International American Joint Distribution Committee.

Together, the Shermans were among Canada's most generous philanthropists and also organized funding of charitable causes through the Apotex Foundation. The couple made numerous multimillion-dollar donations to hospitals, schools and charities and had buildings named in their honour.

The couple's four children have established a charitable foundation named after their parents to continue their philanthropic legacy.