The power company at the centre of the world’s worst nuclear crisis in 25 years is tapping Japan’s biggest banks for an emergency loan of up to Y2,000bn (almost $25bn) as it faces escalating clean-up and rebuilding costs.

Engineers from Tokyo Electric Power have been struggling to contain the situation at the Fukushima nuclear plant since it was damaged beyond repair by this month’s devastating earthquake and tsunami. On Tuesday the Japanese government estimated total rebuilding costs from the twin natural disasters at Y25,000bn – almost 5 per cent of GDP and dwarfing the Y10,000bn spent after the country’s 1995 Kobe quake.

Damage-control operations at the power station were halted on Wednesday after smoke poured from one of the plant’s six reactors, forcing emergency workers and technicians to evacuate. It was the second time in three days that grey smoke from the plant’s No 3 reactor has halted emergency work. Tepco has been unable to identify its source, but said that radiation readings at the plant have not risen noticeably.