A short video clip depicting slippers bearing information on missing children in a supermarket in Zhoukou city, Central China's Henan province, has been hailed by many netizens.

The slippers were manufactured by the Yuntuo factory in Cixi, a county-level city of Ningbo, East China's Zhejiang province. The factory was established by Cai Lei, 43, a Henan native, in 2009.

"I saw Lost and Love, a movie about child trafficking in 2015, and I was determined to do something to help fight the crime," he said.

Since then, Cai has joined the fight against child trafficking by volunteering at baobeihuijia.com (Baby Come Home), China's first nonprofit people finder website.

"I've seen many families posting missing person posters on the street and this made me wonder if there was any way I could help them and let more people see the missing child's information," Cai said during a telephone interview with Ningbo Evening News.

In 2016, Cai contacted the charity and the police departments, and together they created a special tag bearing children's information to be attached to the slippers.

His act of kindness has inspired Mao Wei, general manager of Ningbo Cizhou Technology Network Co Ltd, a Cixi-based shoe maker, to follow suit.

"Seeing how these children cannot reunite with their parents, I thought we ought to do what we can, like Cai," said Mao, who is the father of two children.

To date, the two companies have sold more than 40 million pairs of slippers with labels bearing missing children's information.

Child trafficking is a thorny issue that worries many parents in China.

The country has stepped up efforts against child trafficking, with the Ministry of Public Security setting up a platform to report information on missing children in 2016. By March, the platform had made public close to 4,722 pieces of information and helped find over 4,600 lost children.

However, Cai's efforts also have drawn criticism. Some critics disparaged his campaign as "nothing more than a marketing gimmick".

"If my products are of good quality, and if they can help find lost children, what is the problem?" he responded.

Baobeihuijia.com responded on March 16 that it supports any companies that are willing to help spread missing children's information, which can be done only after approval by public security authorities.