E. coli O157, detected in ground beef that originated from the XL Foods plant is the same strain that killed seven people during the tainted water scandal in Walkerton, Ont., in 2000. (CBC)

Health officials say seven people in Nova Scotia have been infected with a potentially deadly strain of the E. coli bacteria.

Dr. Robert Strang, the province's chief public health officer, said all seven people were infected between Dec. 23 and Dec. 26 — three in Halifax, two in Antigonish, one in Truro and one in Stellarton.

Five people have been treated in hospital and released, while two people remain hospitalized. One is suffering from kidney failure.

Strang said five cases of E. coli O157 have also been reported in New Brunswick, leading health officials to believe the common denominator is likely a food item that is sold in both provinces.

"There's no definitive common source but certainly the pattern of the cases put together looks like some common food product that's been distributed widely," Strang told CBC News.

"We're working with our food safety colleagues in both provinces as well as with the Public Health Agency of Canada to investigate, identifying any further cases and also tracing back potential links in food products to try to identify a common source."

Strang said beyond the existing dozen cases, no new cases have been reported and it's hoped the food item in question is one with a short shelf life.

"Our hope is that this has been a time-limited exposure of some type of a food product like a fruit or a vegetable that has a very limited shelf or market life," he said Thursday.

E. coli O157 is the same strain that killed seven people in Walkerton, Ont. in 2000.

It also led to the biggest beef recall in Canadian history this fall. The Canadian Food Inspection Agency recalled more than 1,500 beef products that were packed at XL Foods, a meat processing plant in Brooks, Alta.

This particular strain of E. coli secretes a powerful toxin that can destroy red blood cells leading to severe illness, high blood pressure and kidney damage.

Symptoms of E. coli O157 resemble gastro-intestinal illness, such as severe cramps, bloody diarrhea, abdominal pain and vomiting.