TOKYO, July 18 (Xinhua) -- The radiation level of the wastewater containing radioactive materials from a nuclear plant in Niigata, Japan was underreported, its operator said Wednesday, stressing that the incident would not cause a safety problem.

    The radiation leak in water discharged into the sea from the Kashiwazaki-Kariwa nuclear power station after Monday's strong earthquake, was initially put at 60,000 Bq and later found to be 90,000 Bq, Tokyo Electric Power Co. said Wednesday, noting the underreport was due to "computation errors".

    The amount of radiation still "falls below the safety standard set by the state and there is no safety problem," a company official said.