Three children in London, Ont., have been infected with a dangerous strain of E. coli, prompting the city's public health agency to warn people not to consume ground beef from a local meat store.

The Middlesex-London Health Unit said Saturday it received the three reports over five days.

"To receive three laboratory confirmed cases of E. coli O157:H7 in such a short time frame is unusual," the Health Unit said in a release.

E. coli, short for Escherichia coli, is a type of bacteria commonly found in the intestines of animals and humans. There are hundreds of strains, but E. coli O157:H7 has been identified as the most dangerous to people, producing a powerful toxin that can cause severe illness.

Two of the infected children consumed spiced ground beef product — known as a kofta — that was purchased from the Westmount Halal Food Store on June 14 and 15, said the Health Unit. It is not immediately clear what the source of the third infection is. That child's family also eats Halal meat, but they did not purchase any food from the Westmount store.

The Canadian Food Inspection Agency is working with London Public Health to isolate the source of the contamination.

The CFIA has also made a number of recommendations to the public:

• Stop consuming ground beef or kofta purchased between June 2 and Saturday from the Westmount Halal food store.
• Those who have developed symptoms of severe or bloody diarrhea should contact the Middlesex-London Health Unit (519-663-5317 ext. 2330, after hours 519-675-7523) and a doctor.
• Those who still have meat purchased from the Westmount store between June 2 and Saturday should contact the Middlesex-London Health Unit.
• Those who have diarrhea caused by E. coli should wash their hands thoroughly or use an alcohol-based sanitizer after using the bathroom or changing the diaper of a baby that has symptoms of the infection.
• The public should ensure that meat is appropriately cooked. The CFIA says ground beef should be cooked to an internal temperature of 71 C.

The Westmount store will provide refunds to affected customers, the CFIA says.

E. coli O157:H7 can contaminate ground beef during the butchering process. If it is present in the intestines of the slaughtered animal, it can get into the meat.

Symptoms characterized by severe abdominal cramping can appear within hours, but could also take up to 10 days to show up. Some people may also be afflicted with bloody diarrhea or non-bloody diarrhea. Frequently, no fever is present.