TOKYO — The company that runs Japan’s crippled nuclear power plant announced Wednesday that it had stopped the leak of tons of highly radioactive water into the ocean discovered over the weekend. The news came a day after the company said the levels of radioactive material in the seawater near the plant were measured at several million times the legal limit.

But even the rare bit of good news from the plant was unlikely to calm worries about the growing contamination in nearby coastal waters. On Tuesday, the government said that a fish caught about 43 miles away was found to have high levels of radioactive iodine 131, prompting it to announce radiation safety levels for fish.

And the company has been flushing thousands of tons of relatively low-level radioactive water into the Pacific to make room in storage containers for increasing amounts of far more contaminated runoff. The runoff resulted from workers’ pouring massive amounts of water on reactors and spent fuel-rod pools to keep them from overheating after their normal cooling systems failed.

The water being intentionally released contains about 100 times the legal limit of radiation, said the Tokyo Electric Power Company, the plant’s operator. The more contaminated water that it hopes to contain has about 10,000 times the legal limit.