Arkansas ? Ten children at an Arkansas day-care center drank windshield wiper fluid after the owner served it from a container mistaken for Kool-Aid and placed in a refrigerator, authorities said Friday.

The day-care owner voluntarily surrendered her state license Friday.

Doctors estimate the children, ages 2 to 7, drank about an ounce of the blue fluid late Thursday afternoon before realizing it tasted wrong, said Laura James, a pediatric pharmacologist and toxicologist at Arkansas Children’s Hospital in Little Rock.

Only one child remained hospitalized Friday in good condition, after blood samples showed “measurable levels” of methanol, a highly toxic alcohol that can induce comas and cause blindness, officials said. In moderate cases, it can cause nausea, vomiting, staggering and sleepiness, James said.

The day care also provided the fluid for testing.

The owner bought the windshield wiper fluid with several other items on a recent shopping trip, James told The Associated Press. “This product was mistakenly grabbed and thought to be Kool-Aid and put in the refrigerator,” she said.