A joint investigation by the HKEx and OM – the supplier and maintenance vendor of the Hong Kong Futures Automated Trading Systems (HKATS) – identified a bug in OM's software when handling certain complex combinations of combo orders. This led to an infinite loop in the transaction process, thereby disabling the HKATS. Trading in the Hang Seng Index (HSI) futures and options, mini-HSI futures and options, MSCI China Free Index futures and Dow Jones Industrial Average futures contracts was brought to a standstill with less than five minutes to go before market close on January 30. Trading in the Hibor futures, three-year, exchange fund notes futures and international stock futures and options contracts was able to resume after a nine-minute halt.