EDMONTON -- More than 60 people across Canada are filing a $500-million class-action lawsuit against the makers of the herbicide Roundup over allegations that its active ingredient can cause cancer.

Toronto-based Diamond and Diamond Lawyers announced the class action lawsuit Wednesday and held news conferences in Edmonton, Vancouver and Toronto.

The lawsuit names Roundup manufacturers Bayer and Monsanto, which were also sued by 18,000 plaintiffs in the United States over similar claims that the product's active ingredient, glyphosate, causes various forms of cancer.

Those lawsuits resulted in the makers of Roundup having to pay damages in excess of $2 billion.

While only around 60 plaintiffs are named in the Canada lawsuit, Diamond and Diamond says thousands of people may be affected.

They're alleging that the makers of Roundup were negligent when they introduced the product into Canadian stores, and withheld that the product carried a risk of cancer.

"It is our belief that the defendants acted negligently in placing Roundup into the stream of commerce in Alberta and elsewhere in Canada," said lawyer Basil Bansal. "We believe that the defendants withheld the risks of cancer and other health risks by secretly ghostwriting scientific journals and providing those to Health Canada."

Bansal alleged safety studies provided to regulatory authorities by the companies named in the suit were "falsified, misleading and included manipulated control groups."

Plaintiffs allege they've suffered various types of cancer include Hodgkin and non-Hodgkin lymphoma, breast, gastric and brain cancer, leukemia and renal cell carcinoma. Bansal said some of the people involved in the lawsuit have since died from cancer, but their estates are still named as complainants.

One Alberta plaintiff, Tony Hunter, said he used the product as a teenager working on his father's farm. He said he has been fighting cancer and cancer-related illnesses for the last 30 years.

"In September 1998, I was diagnosed with Stage 4 non-Hodgkin lymphoma, and I did six to seven months of chemotherapy," he said in a statement read by his wife, Brenda Hunter. His cancer came back in 2005, forcing Hunter to undergo radiation treatments again. After that, he was diagnosed with T-cell lymphoma. Hunter's cancers went into remission but in 2014, he was diagnosed with lupus.

"Although I am grateful to be in remission, my family and I worry about the cancer coming back again," said Hunter. "Growing up, I believed Roundup was a safe product because there were no warnings that indicated otherwise."

In a statement provided to CTV News, Bayer and Monsanto denied allegations that the product causes cancer.

“While we have great sympathy for any individual with health issues, the safety of our glyphosate-based herbicides is supported by an extensive body of science spanning more than 40 years, including numerous studies that have led health regulators around the world to repeatedly conclude that glyphosate is not carcinogenic," the companies said.

They added that Health Canada re-evaluated glyphosate as a chemical as recently as 2017, working with the U.S. Environmental Protection Agency to examine health-related data and scientific studies, and determined the chemical was "unlikely to pose a human cancer risk."

The lawsuit is asking for $500 million across three claims filed in Ontario, Alberta and B.C. 

With a report from CTV News Edmonton's Bill Fortier