The Tokyo Stock Exchange (TSE) has blamed Fujitsu - which is responsible for the development and support of its trading platform - for its worst ever systems crash last week.
TSE was forced to suspend trading of stocks and convertible bonds for more than four hours last Tuesday. At the time the exchange said the shutdown was due to a problem with a system that distributes price information.
In a statement, TSE says the shutdown was caused by the failure of Fujitsu to issue certain instructions linked to a software upgrade carried out last month to its subsidiary, Tosho Computer Systems (TCS).
The exchange says "part of a necessary step was missing in the instruction". This caused a malfunction during a regular monthly clean-up of the dealing system and the error forced the exchange to suspend trading.
Takuo Tsurushima, president and CEO, TSE says the exchange has asked Fujitsu to investigate the issue. He says the exchange is also reviewing its own internal processes and back up measures.
On Friday Japan's Nagoya Stock Exchange was also forced to suspend trading because of a technical glitch with a system that distributes price information.
Following the two incidents Japan's Financial Services Agency ordered the country's six stock exchanges to undertake a review of internal IT systems and file a report on their findings by the end of this month.