The E. coli outbreak in the Maritimes has officially gone national.

Doctors and food inspectors say there is a scientific link between cases in New Brunswick, Nova Scotia and Ontario.

The outbreak appears to be contained in Nova Scotia, but its cause remains a mystery.

'"We've had no new cases in last 24 hours,” says Dr. Frank Atherton, Nova Scotia’s deputy chief medical officer of health. “We still have ten cases of E. coli 0157 in Nova Scotia."

However, there are now six cases of E. coli in New Brunswick - up one from Tuesday.

Doctors say all of the cases, including four in Ontario, are linked.

"Laboratory work has confirmed they are of a very similar strain to the samples from New Brunswick and Ontario. That means we are correct in our assumption that there is a common source to this outbreak," says Atherton.

“We are still carrying on our investigations along two main routes. One is to look at the food histories of all the patients who have been affected. The other is to look at the food stuffs from the restaurants where they had eaten."

Luc Erjavec of the Canadian Restaurant and Foodservices Association says the commonality between the cases could have been a restaurant, but that does not necessarily mean the establishment is not up to standard.

"It has nothing to do with the operation of a restaurant,” says Erjavec. “It is a product purchase from a supplier. We trace it back to the supplier. In this case it seems to be a perishable product. So there's no product left to test because it has either gone bad or been used."

This means that while the risk factor appears to be dropping, detecting the source may prove impossible.

"We are hopeful that whatever it was that caused the exposure has come and gone from the food chain here in New Brunswick," says Dr. Eilish Cleary, New Brunswick’s chief medical officer of health.

In addition to scientific lab work taking place in Winnipeg, investigations in all three provinces are being conducted by the Public Health Agency of Canada and the Canadian Food inspection Agency.

WIth files from CTV Atlantic's Paul Hollingsworth