The amount of yuan held by foreign banks has risen significantly, in anticipation of another rise in the value of China’s currency.
The Chinese government revalued its currency in July, allowing it to trade at a higher rate against the US dollar. Speculators expect the yuan to rise further as China comes under pressure to ease trade tensions with the US.
China’s trade surplus may hit $100bn (¬£56bn) this year, exacerbating its dispute with the US over cheap exports.
Many US politicians say China’s currency is artificially undervalued, giving it an advantage in the export market and threatening US jobs.