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 center 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.

The day care's owner, Carolyn Bynum, was interviewed Friday by child welfare investigators and gave up her license, said Julie Munsell, a spokeswoman for the state Department of Human Services. Bynum declined to comment to the AP, but Munsell said she accepted "total responsibility" for the incident.

"She was so upset about what had occurred and she was definitely worried some of the children had been injured," Munsell said. "It was just a mistake, she says. She says it was just a horrible mistake."

Bynum's license had allowed her to care for 10 children in her home in Scott, east of Little Rock. Munsell said Bynum had no found complaints or serious compliance issues since receiving the license in 2002.

By surrendering her license, Bynum can no longer care for the children without reapplying. State law requires a license when someone cares for more than five children from more than one family at the same time in their home.

The toxicologist warned that many antifreeze or windshield wiper solutions have bright colors, which can be mistaken for fruit drinks.

"I think the take-home message is not to have these products in the kitchen or where you're doing any kind of food preparation," she said.