XI'AN -- A kindergarten in Xi'an in Northwest China's Shaanxi province was closed on Wednesday after parents disclosed the school has long been administering antiviral drugs to children.

Police have put the private kindergarten's legal representative, principal and kindergarten doctor into custody, a joint investigation team with Xi'an government authorities confirmed on Wednesday.

The team was jointly assembled by the city's police, education, health, and pharmaceutical supervision authorities after a parent on Sunday said in a microblog that the Fengyun Lanwan Kindergarten had been giving kids the prescription medicine moroxydine ABOB for years.

The parent said that the kindergarten delivered the drug without notifying parents.

Dozens of parents on Tuesday gathered and blocked the road in front of the kindergarten demanding an explanation.

Some parents told Xinhua their kids were experiencing discomfort with several symptoms, including dizziness, leg pain and stomachaches.

They said that the kindergarten administered the drug to ensure the children's attendance, as nursery fees were charged based on the number of days attended.

Parents were anxious to know how large a dose children were given and for how long, as well as the possible harmful side effects and need for follow-up physical examinations.

"Even starting when she was in the lowest class years earlier, teachers started giving them the medicine two or three times weekly with a tablet each morning and evening," said a mother surnamed Wang, who has a five-year-old daughter in the upper class of the kindergarten.

Her daughter has shown some symptoms such as dizziness and leg pain.

Another mother surnamed Zhang said her 6-year-old daughter complained of feeling dizzy and having leg pain and stomachaches.

"I also found my daughter has had constipation, night sweats and excessive discharge in her private parts," said Zhang.

The joint team of government authorities has conducted an initial investigation.

It confirmed that the kindergarten has given kids prescription medicine that may cause adverse reactions of sweating, loss of appetite and hypoglycemia.

The school's actions are unlikely to cause accumulated harmful effects as the amount given to most of the children has not exceeded the specified dose. However, the dose given to the lower class was slightly excessive.

The Xi'an municipal government has submitted the medicine for further testing and ordered medical experts to conduct analysis and assessment of the drug's effects on humans.

The government will also offer free physical examinations for kids with symptoms.