(Photo/Youtu Lab)

Chinese police have, for the first time, found missing children using AI facial recognition, bringing a message of hope to parents who have lost their children.

Four children who had been missing for around 10 years were identified using the technology, marking a remarkable breakthrough.

"I'm surprised, I can't believe it," said Li Xin, an expert who worked at the police department for eight years and now works as a consultant of a program which tracks missing children, conducted by Chinese tech firm Tencent.

A kid nicknamed Xiaohaozi (little mouse in English) was among the four children found on this occasion. The child went missing in June 2009 in Wusheng county, southwestern China's Sichuan province. It was a living nightmare for his parents, who run a restaurant in the county.

The couple kept their restaurant open, to help save enough money to allow them to travel the country in search of their son.

"Over the past 10 years, we had chances to move our business to other places, but we chose not to," said Gui Hongzheng, Xiaohaozi's father, adding that had hoped their son would remember the restaurant and return in the future.

For the past decade, the anti-trafficking office of Sichuan Provincial Public Security Department, as well as inferior branches, have been actively searching for Xiaohaozi, together with nine other missing children.

Fortunately, the facial recognition technology of Youtu Lab under Tencent, which can detect gender and age, gave the police officers a valuable opportunity. In December 2017, the technology was introduced in the Sichuan Provincial Public Security Department.

Tencent quickly gained rich experience in AI-aided measures to find missing children. By October 2018, a Tencent program has found over 600 missing people, and Youtu's AI face detection technology has helped the Fujian police department find over 1,000 people to date.

However, the task was still arduous, said Li.

"Xiaohaozi was only three years old when he went missing, and had turned 11 by the end of 2017," said Li, adding that there had been no case of finding a child who had been missing for over 10 years through facial recognition technology.

Li and his colleagues applied an innovative method by using machines to teach machines. After tens of thousands of tests, they finally trained a neural network model that could recognize human faces despite age differences, with an accuracy of over 96 percent.

Xiaohaozi was found in southern China's Guangdong province in April, and the family has since been reunited.

According to Li, his team is still working to improve the performance of the model, and the accuracy now stands at over 99.8 percent.