Shanghai police on Nov 8 detained three suspects in a child abuse case that took place at online travel agency Ctrip's in-house day care center.

The suspects - a cleaner, a child-care worker and the teacher in charge of the class – have been charged with child abuse. The head of the day care center, who is not detained, is being charged with dereliction of duty.

Video evidence of the child abuse went viral on the Internet on Nov 6. Ctrip alerted police to the incident on Nov 7.

The footage shows that teachers at the day care center were rough in their handling of the children, causing some to fall and suffer injuries. Some children were also forced to swallow items which was later identified as mustard. According to the police, the children involved in the case are aged between 18 and 24 months.

All classes in the kindergarten have been suspended since Nov 9.

The operations of the day care center is managed by a company called Modern Family Magazine. The Shanghai Women's Federation, which is the shareholder and direct supervisor of the company, announced on its official Weibo account on Thursday that it will "deal with the incident seriously and strengthen management of its subordinate units."

The federation also said that the day care center has sacked the four suspects and apologized to the families of the affected children.

On Nov 8, the top management of Ctrip apologized over the incident and said it would continue assisting the police in their investigations.

"On behalf of the company, I extend my sincere apologies to the involved families and children," said Sun Jie, CEO of Ctrip.

According to Sun, Ctrip has also set up an investigation team which will review the day care center's surveillance footage in the past three months.