Washington health officials said Tuesday that they are investigating a cluster of polio-like illnesses in the state, as nine children have now been hospitalized and a 6-year-old boy has died.

The Seattle Times reported that a spokeswoman for the state's health department confirmed two of the nine children hospitalzed tested positive for a rare virus known as acute flaccid myelitis, or AFM. The department says the children all had loss of strength or movement in one or more of their limbs. In October, the Centers for Disease Control and Prevention (CDC) reported a rise in AFM cases from 2015 to 2016.

"There’s nothing that points to an individual cause for any of the cases or a link between the cases," Julie Graham told the Seattle Times. The children range in age from 3 to 14.

The boy who died over the weekend, Jonathan Daniel Ramirez Porter, known as Daniel, of Bellingham, was suspected to have AFM. His family shared Daniel's plight on Facebook and a GoFundMe page a relative had set up to raise funds for his medical care.

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Doctors say AFM is not contagious, but there is no vaccine for it. The illness appears to be an abnormal reaction to various ailments, including West Nile virus and the common cold.

Ramirez's parents told local media that he was sent to the hospital with cold symptoms and dizziness. He was paralyzed within a few hours and never recovered.

Officials said that five of the children had been released from local hospitals. 

Two AFM cases were recorded in Washington state two years ago. One of those patients remains paralyzed from the neck down.