TORONTO -- Both the federal and Ontario governments say it's not clear how many companies like the one that supplied diluted cancer drugs to five hospitals in Ontario and New Brunswick are operating in Canada.

Ontario Health Minister Deb Matthews acknowledged Wednesday that she doesn't know how many companies like Marchese Hospital Solutions are operating in Ontario and mixing drugs for hospitals.

Finding that out is part of the investigation into the province's cancer drug supply that's already underway, she said.

"This is not confined to Ontario," she said.

"My big responsibility is to Ontario patients, that's why I'm taking this so seriously. That's why I've established this group, even though it's pretty clear that this is a national and indeed an international problem."

Health Canada said last week that it's aware of at least one other company like Marchese operating in Ontario.

"Health Canada is working in partnership with the province to determine the exact activities of Marchese Hospital Solutions with regards to admixing of chemotherapy drugs," spokeswoman Leslie Meerburg wrote Wednesday in an email.

"Once that is determined, we will be in a better position to discuss other companies that have similar practices."

Too much saline was added to the bags containing cyclophosphamide and gemcitabine, in effect watering down the prescribed drug concentrations by up to 20 per cent.

More than 1,200 cancer patients in Ontario and New Brunswick received the diluted drugs, some for as long as a year. But Matthews said the problem is limited to the five hospitals that used Marchese Hospital Solutions.

Ontario's New Democrats say it's disturbing that the provincial government doesn't know how many companies like Marchese -- which had no oversight -- are operating in Ontario.

"We don't know if this is happening with other kinds of chemotherapy drugs, but we don't know whether it's happening with other kinds of drugs either," said NDP Leader Andrea Horwath.

"And that's a pretty frightening prospect for Ontario's patients."

It also raises questions about whether the privatization of hospital work -- like drug mixing -- has gone too far, she said.

Matthews chastised the NDP for "politicizing" the issue, but suggested that the federal government should be more involved.

"Many will argue that this is an issue that should be led by Health Canada," she said in the legislature.

Marchese Hospital Solutions fell into a jurisdictional grey area, with Health Canada and the Ontario College of Pharmacists unable to agree on which was responsible for the facility.

Hospitals are responsible for the purchase and security of their drugs. Health Canada regulates and inspects drug manufacturers, while the college is responsible for pharmacists in Ontario, including those who may have been working independently for the company.

But Marchese Hospital Solutions, which was federally incorporated, wasn't considered to be a pharmacy or a drug manufacturer.

The need for clarity is an issue Health Canada has been dealing with for at least a decade.

A 2009 policy paper cited "a need to develop a Canada-wide consistency in approach to ensure that drug compounding and manufacturing are each regulated by the appropriate authorities."

The diluted drugs were only discovered when a pharmacy technician at a hospital in Peterborough -- which had just switched over to Marchese -- noticed that the bags were overfilled, a legislative committee heard Tuesday.

The hospital then got in touch with another one in Oshawa that was using the same supplier.

There are other companies that provide mixed chemotherapy drugs to hospitals, said Michael Sherar, CEO of Cancer Care Ontario. But he didn't have a complete list.

"We are trying to find out who's in the industry, because the unregulated aspects -- in other words, who are not pharmacies -- it's hard to know who else is out there," said Saad Rafi, deputy minister of Health.

How Marchese Hospital Solutions has structured itself to combine or prepare the chemotherapy drugs is a "unique circumstance," he said.

Marchese Hospital Solutions had an accredited pharmacy in the same building where the mixing was done, college registrar Marshal Moleschi told the committee.

Two pharmacists with Marchese have been questioned by the college as part of its investigation, which could take a few months, he said.

Marchese has said its products weren't defective, and suggested that the problem wasn't how the drugs were prepared but how they were administered at the hospitals.