Since blogger Xu Alun released this documentary on February 10, it's had over half a million hits. It tells the story of three homeless orphans working as coal-haulers in a southern city of China. According to our Observer in Hong Kong, a specialist in social problems in China, this is just one example of millions of "left-behind children" in the country.

"This work is strictly illegal. The minimum working age in China is 16"

Robin Munro works for the China Labour Bulletin and is a specialist in social problems in China. He lives in Hong Kong:

The parents of these children are probably migrant workers who left home to find work in a big city. One hundred and fifty million people are on the move in China, and most of them have left their children with relatives or friends. We call them "left behind children". In many cases they're not looked after and many run away. They try to find their parents but they don't know where to look. They're extremely vulnerable to labour gangs; they're a very important source of cheap labour.

This work is strictly illegal. The minimum working age in China is 16, and until 18 these "juvenile workers" are supposed to be protected from heavy industry, construction or mining work. But a rising number of 14-16-year-olds are dropping out of school, largely due to the fees charged in the rural education system. Children usually drop out because of financial pressure. But at such an early age as the children in the video [some started at 8 or 9], well, we think that's unusual; though we really don't know.

The Chinese government does not publish figures or data on child labour. It's considered a "state secret", and one could go to jail for publishing any information about it. They simply won't admit to a child labour problem; it's considered a social embarrassment.

Posting these videos could be extremely dangerous. He [Xu Alun] seems to have got away with it this time. The government often gets hold of a video early enough to delete it, but in this case it had already attracted too much attention and they acted constructively by getting involved. However it doesn't solve the [overall] problem. These children are educationally stunted and their prospects- if they make it through childhood - are very grim. Working at such an early age will leave them with permanent scars."

The first part of Xu Alun's documentaryThe Child Coal Hauler,posted on 10 Feb.08

Creator Xu Alun says he made the videos to highlight the problem of child labour in China. He then posted the documentary on a Chinese video sharing network. It caused such a stir online that donations for the children began flooding in. The growing pressure forced local authorities to get involved and the children have since been removed from their work and put into schooling. The story was reported by Global Voices.