A recent outbreak of a potentially deadly strain of E. coli at a Washington state day care center has killed one child and sickened three other children, health officials said.

The child who died was a 4-year-old boy, said Elizabeth Winter of the Washington state Department of Early Learning. The department was notified of his death on Friday, she said.

The boy was hospitalized on March 19 after he was struck by the E. coli O157:H7 bacteria, said Dr. Alan Melnick, the health officer for Clark County, Wash. The other three children were hospitalized soon afterward and have since been released, he said.

County public health officials temporarily closed the home-based, licensed day care center operated by Dianne and Larry Fletch on April 2.

The Vancouver day care has operated since 1990 and has had no complaints filed against it, Winter said.

Health officials said they don't know the precise source of the outbreak. But they said it didn't appear related to food, water or another single source.

E. coli O157:H7 is a potentially deadly bacterium that can cause bloody diarrhea and dehydration. The very young, seniors and people with compromised immune systems are the most susceptible.