According to police, the two suspects, Shi Haixia and Yang Wenming, admitted that they injected the poison into the yogurt and left it on the street. Their intention was to damage the reputation of the rival kindergarten.

Shi, the head of the other kindergarten, had disputes with the girls' kindergarten over the enrollment of new students. She injected the poison into the yogurt and asked Yang to place it with some notebooks on the way to the rival kindergarten on April 24.

The two suspects were arrested on Wednesday and the case is under investigation, police said.

A publicity official from the county government, who declined to be named, said the government is working on measures to protect the children. All kindergartens in the county will be asked to check their food.

Yuan Ailing, a professor of primary education from the School of Life Sciences at the East China Normal University, said, "This is an extreme case showing the lack of supervision in preschool education."

Like child-abuse cases exposed frequently, the case stemmed from the lack of effective supervision from local governments, she said.

"Though many departments have their responsibilities in the management of kindergartens, they didn't perform their coordinated supervision duties well," she added.

Insufficient investment in public kindergartens led to a shortage of vacancies. Private kindergartens were set up to fill the void, and many of them don't have enough money to hire qualified teachers, meaning that they can't attract enough students.

"The local governments need to increase the financial support for kindergartens, and control the new private ones if the districts have enough kindergartens," Yuan said.

Many governments have started to increase the number of public kindergartens in recent years. In Beijing, some 118 new public kindergartens will open by the end of 2013. Guangdong province has also released a similar plan, pledging to build public kindergartens, so that they account for 30 percent of the total by 2013.

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