Workers at the stricken Fukushima nuclear plant in Japan have resumed their efforts to restore electrical power and cool its overheated reactors.

The work was interrupted after emissions of white vapour and smoke from two of the reactors.

Japan's Chief Cabinet Secretary says it is impossible to say what's causing the steam and hazy smoke because the plant's operators cannot see what is going on inside the buildings housing the reactors.

The BBC's Chris Hogg reports from Tokyo.