Please answer a question about the following article about Child labour:

BBC, in 2012, accused Glencore of using child labour in its mining and smelting operations of Africa. Glencore denied it used child labour, and said it has strict policy of not using child labour. The company claimed it has a strict policy whereby all copper was mined correctly, placed in bags with numbered seals and then sent to the smelter. Glencore mentioned being aware of child miners who were part of a group of artisanal miners who had without authorisation raided the concession awarded to the company since 2010; Glencore has been pleading with the government to remove the artisanal miners from the concession.

What did the BBC say that Glencore used child labour for in 2012?
mining and smelting operations of Africa