The mother of a boy whose teacher was photographed holding him up by his ears, has vowed to sue the kindergarten after the teacher was released from police custody with no criminal charges being laid, local media reported.

The mother of the boy, from Wenling city in East China's Zhejiang province, said she was shocked that the teacher was not found guilty of child abuse, Hangzhou-based City Express reported.

Kindergarten teacher Yan Yanhong was detained by police after a photo of her holding the boy by the ears circulated online, but she has now been released without charge, according to a statement on the official micro blog of public security bureau, posted on Friday.

The police bureau said in the statement that it has withdrawn the criminal case after a detailed investigation against Yan found she had not committed acts that constitute a crime according to the basic principle in the Criminal Law.

Yan and another teacher were arrested by police on Oct 25 for creating a disturbance after posting photos online of Yan picking a child up and holding him by the ears and sealing another boy's mouth with tape, sparking anger from netizens.

The Constitution and laws on compulsory education and the protection of minors contain relevant items regarding child abuse, but there are no specific items on child abuse in the Criminal Law.

The mother of the boy being held in the photo, surnamed Lin, said she was shocked that the two teachers were released without criminal charges.

"It is so unfair that the teachers who abused the children for fun will not be punished for their bad behavior, and it will not act as a deterrent to other teachers involved in similar cases," said Lin, who has sent her son to another kindergarten. She claimed she would file a lawsuit against the kindergarten.