Tokyo Electric Power Co (Tepco) is assessing a government report that highlights the threat of another tsunami overwhelming its wrecked Fukushima nuclear station, the company said on Wednesday.

Tepco is trying to clean up the site of its Fukushima Daiichi plant, hit by a massive earthquake and tsunami in 2011, an effort expected to last decades as it looks to build defences against another disaster.

The latest government projection suggests an 11-metre (36-ft) seawall planned by Tepco engineers could be overwhelmed if tsunami waves taller than 20 metres (66 ft) are unleashed by a quake of magnitude 9 or more, broadcaster NHK has said.

“Tepco will examine the latest projections and analyse the impact on the ongoing preventive measures against tsunamis that the company has been taking,” a spokesman told Reuters by telephone.

The earthquake that struck off Japan’s east coast in March 2011 had a magnitude of nine, spawning a tsunami that led to the meltdown of three reactors at Fukushima, where Tepco continues to struggle to curb release of radioactive material.