The Japanese nuclear energy watchdog raised the incident level from one to three on the international scale that measures the severity of atomic accidents.
This was an acknowledgement that the power station was in its greatest crisis since the reactors melted down after the tsunami in 2011.
But some nuclear experts are concerned that the problem is a good deal worse than either Tepco or the Japanese government are willing to admit.
They are worried about the enormous quantities of water, used to cool the reactor cores, which are now being stored on site.
Some 1,000 tanks have been built to hold the water. But these are believed to be at around 85% of their capacity and every day an extra 400 tonnes of water are being added.
“The quantities of water they are dealing with are absolutely gigantic,” said Mycle Schneider, who has consulted widely for a variety of organisations and countries on nuclear issues.
“What is the worse is the water leakage everywhere else – not just from the tanks. It is leaking out from the basements, it is leaking out from the cracks all over the place. Nobody can measure that.
[How many times do we need to go down this road? And guess where that sea water is headed?]