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Investigators believe a billionaire couple found dead in their mansion last month were murdered, Toronto police announced Friday.

Barry Sherman, the founder of the Canadian drug company Apotex, and his wife, Honey, were found dead in their mansion on Dec. 15. Police at the time called the deaths suspicious, but said there were no signs of forced entry.

But after six weeks of investigation, authorities now believe they have a double homicide on their hands, Det. Sgt. Susan Gomes said on Friday. She declined to discuss evidence, possible motives or suspects.

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Related: Deaths of billionaire and his wife investigated by homicide detectives

The Shermans were found dead in a pool area, “hanging by belts from a poolside railing in a semi-seated position on the pool deck,” Det. Sgt. Susan Gomes said on Friday.

“They were wearing their clothing,” Gomes added.

The couple was last seen alive on the night of Dec. 13, and their bodies were discovered two days later, according to Gomes.

In a statement to the Associated Press, the Sherman family said the murder conclusion “was expressed by the family from the outset and is consistent with the findings of the independent autopsy and investigation.”

“The family continues to support the Toronto Police Service in their efforts to seek justice for their parents and pursue those responsible for these unspeakable crimes,” the statement said.

Gomes said the family had been frustrated with the police.

“For them, it has been difficult to balance their patience with their frustration with us and our investigation, not unlike any other family who has suffered such a sudden and profound loss,” she said.

“They have been understanding, cooperative and hopeful that this investigation can give them some answers,” she added.

Barry Sherman, 75, founded Apotex in 1974 as a two-person operation. The drugmaker now employs 11,000 people worldwide, according to its website.