Levels of radioactivity have risen sharply in seawater near the Fukushima Daiichi nuclear plant in northern Japan, signaling the possibility of new leaks at the facility, the Japanese government said Saturday.

The announcement came after a magnitude-5.9 earthquake jolted Japan on Saturday morning. There were no immediate reports of damage and tsunami alert after the earthquake.

The Tokyo Electric Power Company, which runs the radiation-leaking Fukushima plant, recently discovered and eventually plugged a leak that could have been gushing for days. It said levels of radioactive materials in the seawater near the plant dropped after that.

But the government said levels of radioactive materials in the seawater have risen again in recent days. The level of radioactive iodine 131 jumped to 6,500 times the legal limit, according to samples taken Friday, up from 1,100 times the limit in samples taken the day before. Levels of cesium 134 and cesium 137 rose nearly fourfold.

The increased levels are still far below those recorded earlier this month before the initial leak was plugged, according to a New York Times report.

The crisis has forced tens of thousands of people to evacuate the area, while radiation leaks have contaminated crops and left fishermen unable to sell their catches, adding to the suffering of communities already devastated by earthquake and tsunami damage, China Daily reported.

The Japanese National Police Agency said on Thursday that the March 11 earthquake and tsunami have left 13,498 people dead and 14,734 others unaccounted for in Japan by 19:00 p. m. local time (1000 GMT).

A 9.0-magnitude earthquake hit the Pacific coastal areas of northeastern and eastern Japan on March 11, triggering enormous tsunami.