Assets at the Exchange Fund,which is used to back the Hong Kong dollar,totalled HK$2,646.5 billion ($341.5 billion) at the end of September,the Hong Kong Monetary Authority (HKMA) said on Wednesday. The figure was HK$85.8 billion higher than the total at the end of August,with foreign currency assets and Hong Kong dollar assets rising HK$49.1 billion and HK$36.7 billion respectively,the city's de facto central bank said in a statement. The HKMA said the rise in foreign currency assets was mainly due to increases in Certificates of Indebtedness and unsettled purchases of securities,purchases of foreign currencies with Hong Kong dollars and valuation gains on foreign currency investments. The rise in Hong Kong dollar assets was mainly due to increases in bank borrowings and Exchange Fund Bills and Notes issued but not yet settled,and valuation gains on Hong Kong equities. These increases were partly offset by fiscal drawdowns.