The problems come as demand for cash rises in the wake of Friday's earthquake and subsequent tsunami as well as the ongoing fears surrounding the damaged Fukushima Daiichi nuclear plant. The cause of the problems has yet to be established but Mizuho president Satoru Nishibori told a press conference today a surge in transactions may be behind them, while a spokesman told the WSJ that the power cuts caused by the earthquake are not thought to be responsible. Local news outlet Nikkei says that another possible explanation is the systems changes recently made to enable ATMs to accept earthquake relief donations. No other major financial institutions have reported problems. In the wholesale markets, The Tokyo Stock Exchange and Japanese financial regulators have resisted calls from foreign banks to halt trading as the markets bucked wildly in the wake of the crisis. The TSE has stood firm throughout the week, relying on its new Arrowhead trading platform to handle spikes in capacity during volatile trading.