An E. coli outbreak linked to a restaurant in northeastern Oklahoma has?hit more than 200 people and killed at least one, CNN reported on Wednesday.

In all, 206 people, including more than 50 children, are sick as a result of the outbreak. State health investigators are testing at the Country Cottage restaurant in Locust Grove, about 50 miles (80 km) east of Oklahoma's capital Tulsa.

But an exact source of the contamination has not been pinpointed. What makes it hard for investigators is it is a form of E. coli unlike anything they've seen before.

The subtype of bacteria -- called E. coli 0111 -- is "not normally found in this form of outbreak," said Leslea Bennett-Webbof Oklahoma State Department of Health.

Symptoms of infection with the bacteria can include severe diarrhea, vomiting and abdominal cramping. The U.S. Centers for Disease Control and Prevention estimates there may be about 70,000E. coli infections each year in the United States. 　

(Xinhua News Agency September 4, 2008)