Canadian police have arrested and charged a Toronto-area man they allege is linked to deaths by suicide in Canada, the UK and the US.
Kenneth Law, 57, is facing two counts of counselling and aiding suicide.
Peel Regional Police believe he may have sold a lethal substance online, with packages going to people in over 40 countries.
His arrest comes after a recent Times investigation linked him to at least four deaths in the UK.
Police said on Tuesday they began investigating the case a month ago following the sudden death of an adult in the Toronto-area.
Mark Andrews, deputy chief of community policing for the Peel police, said authorities believe the person ingested a lethal substance that was sold to them by Mr Law.
During the investigation, police say they became aware of a second local death allegedly linked to Mr Law, who is accused of operating several companies that provide sodium nitrate. It's a chemical substance commonly used as a food additive that can be deadly when ingested in certain quantities.
Deputy Chief Andrews said his police force is now working with other forces in Canada and internationally to determine if more charges might be be laid. A tip line has been set up for people to come forward with any information.
"We believe there could be more victims," he said.
He added police are aware of 1,200 packages sold by Mr Law that were shipped to over 40 countries, though they do not know how many may have included the substance.
A report published by the Times of London last week linked Mr Law to up to seven deaths, including a 17-year-old boy in the US and four adult British citizens.
One of them was 23-year-old Neha Raju, who died in the Surrey area last April. A coroner's inquest into Ms Raju's death revealed that she died after ingesting a substance that she purchased online.
The inquest said the substance is "freely available to be purchased from the internet in lethal quantities for delivery within the UK", and that "no protection is afforded to vulnerable people prior to them making such purchases".
Doctors in Canada have called for tighter regulation of sodium nitrate.
Speaking to the Canadian newspaper The Globe and Mail last week, Mr Law defended his actions and said that he sold a legal product.
"What the person does with it? I have no control," he told the newspaper.
Mr Law is now in custody awaiting a bail hearing. His first court appearance has been scheduled for Wednesday.
Under Canada's criminal code, counselling or aiding a person to die by suicide can result in a 14-year prison sentence.