A child consultation center in Sagamihara, Kanagawa Prefecture, said Tuesday it stripped eight girls naked to conduct a body search in August to look for a piece of paper that went missing earlier that day.

Center officials later apologized to the girls, saying it was a violation of their human rights and was inappropriate.

According to the center, a piece of paper for use in the suggestion box went missing in August.

Because the welfare ministry's guidelines state that child consultation centers need to make sure that they protect the privacy of their children, who come from problematic families, the center restricts the use of paper for children. At the time of the incident, the girls were under temporary care at the facility.

Children are told not to tell anyone at the center their full names or exchange telephone numbers. The center does not allow children to use pencils and paper except when they are studying.

Center officials said they went to such great lengths to find the missing paper because earlier this year in a different case, a girl at the center wrote down the details of another girl's Twitter account and hid the paper in her underwear.

To find the missing piece of paper in the more recent incident, two female officials, who had the approval of their supervisor, took eight girls between the age of 8 and 15 to the bathroom one by one and stripped them. They used bath towels to hide their private parts, the center said.

Two male officials also conducted body searches of nine boys between the ages of 9 and 15 without stripping them, it said.

The piece of paper was never found.

"It was meant to prevent them from exchanging personal information," a center official said.

One of the girls later complained to another center official, which brought the incident to light.

Officials in the Sagamihara Municipal Government said they will do their utmost to prevent a recurrence.