Fears of a Chinese banking crisis are growing, as a key indicator of the country's debt reaches its highest level on record. China's credit-to-GDP gap hit 30.1% in the first three months of this year - far above the 10% level associated with banking risks - according to a quarterly report by the Bank for International Settlements (BIS). It was also higher than any of the 42 other countries in the BIS survey, including the US, Greece and the UK.