Two of the children, a 6 year old and a 2 year old, are in intensive care as of Monday night. The third child, a 4 year old, is said to be not as sick.
Officials say their family had recently moved to Clark County, and had been living on a farm.
Laboratory tests confirm the oldest and youngest of the three are infected with E. Coli 0157:h7, one of the most serious strains of the food borne bacterium.
Unconfirmed reports say the two have developed a complication called Hemolytic Uremic Syndrome, which puts them at risk for kidney failure.
Doctors are not releasing the family's name, because of federal patient privacy laws.
But they do say the family moved to Clark County less than two months ago. They have been living with the children's grandparents on a farm, surrounded by animals and streams. Doctors say that's a possible tip off as to how they contracted E. Coli.
Clark County Health Department officials say this is an isolated incident, and there is no link with any restaurants, or other public facilities.