The operator of a Japanese nuclear plant where four workers died this week is shutting down all 11 of its nuclear facilities for inspection as it fights allegations of negligence.

Kansai Electric runs the plant at Mihama where the employees were scalded to death when a corroded cooling pipe exploded on Monday. Seven other workers were injured.

Its operations amount to one-fifth of Japan's 52 nuclear power stations.

After Monday's accident, Japan's Nuclear and Industrial Safety Agency told Kansai and six other privately owned utilities to review their inspection records of cooling pipes.

Kansai went further, ordering a temporary shutdown of its 11 plants in western Japan for safety checks.

The company acknowledged Tuesday that the pipe responsible for the accident at Mihama had not been thoroughly checked, though inspectors warned last year that it could be dangerous.

A Japanese cabinet minister said "punitive action" would likely be taken against Kansai as a result.