Radiation was found in groundwater just outside Japan's stricken nuclear plant at 10,000 times the normal limit, officials at the plant announced late Thursday.
The news comes as Japan's nuclear and humanitarian crisis following a 9.0 earthquake and tsunami stretched into the third week.
The operator of the Fukushima Dai-ichi nuclear power plant said in a statement that a test of groundwater revealed radioactive iodine-131 at 10,000 times the limit Japan sets for seawater, the Wall Street Journal reports.
They do not believe it has contaminated the drinking water supply, PBS reported.
A spokesman for the plant operator, Tokyo Electric Power Co., said shortly thereafter that the findings could be an error and more testing will be done.
The report, based on a sample taken near the cement containment foundation of reactor No. 1 at a depth of about 15 meters, would be the first contamination found in groundwater, according to the Journal.
The groundwater report comes as Japan's Ministry of Health, Labor and Welfare announced Thursday that radiation higher than the regulatory limit was found in beef from the Fukushima prefecture near the plant, CNN reported.
The ministry said the beef will not be sold and will be retested.
Japan's Nuclear Safety Commission's guidelines limit the amount of Cesium to 500 becquerels per kilogram, but the beef tested had a total of 510 becquerels per kilogram.
The sale and transport of some vegetables from the area have already been banned.
As Japan struggled to get the crippled plant and radiation under control, France called for new global rules to govern nuclear energy and suggested a global conference in France in May, Reuters reports.
"We must look at this coldly so that such a catastrophe never occurs again," said French President Nicolas Sarkozy during a visit to Tokyo Thursday.
France is the most nuclear-dependent country in the world.
Earlier this week, the U.N. nuclear watchdog told Japan it should consider expanding its evacuation zone around its crippled nuclear power plant as the country's emperor and empress visited evacuees.
The International Atomic Energy Agency (IAEA) said it found radiation measurements exceeding the criterion for evacuation 40 kilometers (25 miles) from the Fukushima Dai-ichi plant in the village of Iitate.
"We have advised (Japan) to carefully assess the situation and they have indicated that it is already under assessment," Denis Flory, a deputy director general of the IAEA.
Japan's evacuation zone is currently 20 kilometers from the plant. It advises those up to 30 kilometers away to leave as well, and if they do not, they should remain indoors.
The United States and Germany are sending robots to help Japan repair and explore its crippled plant, and 140 U.S. military radiation safety experts will soon visit Japan to offer help, Reuters reports.
The earthquake and tsunami that devastated much of the country on March 11 and triggered a humanitarian and nuclear crisis left nearly 28,000 people dead or missing.
-- Hanna Ingber Win