The U.S. Senators from Iowa and Minnesota are asking for an investigation into a rare polio-like illness that has infected seven children across both states.

DFLers Amy Klobuchar and Tina Smith and Republicans Chuck Grassley and Joni Ernst sent a letter to the Centers for Disease Control and Prevention urging it to look into recent cases of AFM, a nervous system condition that weakens victim’s muscles and causing other symptoms similar to polio. It was announced on October 5 that six Minnesota children had developed the disease since mid-September and a case in Iowa was announced on October 10.

“In recent weeks seven children have been diagnosed with AFM in Minnesota and Iowa, including two children who required treatment in the intensive care unit for respiratory support,” the senators write. “Because the causes of AFM are unknown, we urge the CDC to provide more information immediately about preventive measures and treatments.”

The full text of the letter to CDC Director Dr. Robert Redfield as well as the full article can be found here.