The operator of Japan's stricken Fukushima nuclear plant said Monday it planned to dump thousands of tons of radioactive water into the Pacific, as the government was accused of covering up the extent of radiation levels.

"We have no choice but to release water tainted with radioactive materials into the ocean as a safety measure," Yukio Edano, the government’s chief spokesman told a new conference.

The Jiji press agency reported that a TEPCO spokesman said the 11,500 tons of water were only weakly radioactive and that the release would take place "as soon as necessary preparations are made."

The broadcaster NHK reported Monday that the Japanese government withheld the release of data showing that radiation exceeded safe levels more than 18 miles from the plant, beyond the 12-mile evacuation zone.

Computer projections taken March 16 showed that people from as far away as 18 miles from the nuclear plant would be exposed to more than 100 millisieverts of radiation if they were outdoors for 24 hours between March 12 and 24.

Workers used a milky white dye Monday to frantically try to track path of highly radioactive water flowing out into the ocean, but it is not clear how much water has leaked from the pit so far and where exactly it has gone.

A crack in a maintenance pit found over the weekend was the latest confirmation that radioactivity continues to spill into the environment. The leak is a symptom of the primary difficulty at the Fukushima Dai-ichi complex: Radioactive water is pooling around the plant and preventing workers from powering up cooling systems needed to stabilize dangerously vulnerable fuel rods.

Engineers have turned to a host of improvised and sometimes bizarre methods to tame the nuclear plant after it was crippled in Japan's magnitude 9.0 quake and tsunami on March 11. Efforts over the weekend to clog the leak with a special polymer, sawdust and even shredded newspapers failed to halt the flow at a cracked concrete maintenance pit near the shoreline.

Suspecting they might be targeting the wrong channel to the pit, workers tried to see if they could trace the leak's pathway by dumping into the system several pounds of salts used to give bathwater a milky hue, plant operator Tokyo Electric Power Co. said Monday.

"There could be other possible passages that the water may be traveling. We must watch carefully and contain it as quickly as possible," said Hidehiko Nishiyama, a spokesman for the Nuclear Safety and Industrial Agency.

Radioactive water has pooled up throughout the Fukushima Dai-ichi plant because the operator has been forced to rely on makeshift ways of pumping water into plant — and allowing it to gush out wherever it can — to bring down temperatures and pressure in the reactor cores.

Government officials conceded Sunday that it will likely be several months before the cooling systems are completely restored. And even after that happens, there will be years of work ahead to clean up the area around the complex and figure out what to do with it.

The makeshift system makes it difficult to contain the radiation leaks, but it is aimed a preventing fuel rods from going into a full meltdown that would release even more radioactivity into the environment.

"We must keep putting water into the reactors to cool to prevent further fuel damage, even though we know that there is a side effect, which is the leakage," Nishiyama said. "We want to get rid of the stagnant water and decontaminate the place so that we can return to our primary task to restore the sustainable cooling capacity as quickly as possible."

The crisis has unfolded as Japan deals with the aftermath of twin natural disasters that decimated large swaths of its northeastern coast. Up to 25,000 people are believed to have died in the disaster, and tens of thousands lost their homes. Thousands more were forced to flee a 12-mile radius around the plant because of the radiation.

Over the weekend, an 8-inch-long crack was discovered in a maintenance pit, sending a stream of water into the sea. The area is normally blocked off by a seawall, but a crack was also discovered in that outer barrier Monday.

While radioactivity is quickly diluted in the ocean, a government spokesman said Monday that the sheer volume of contamination is becoming a concern.

"Even if they say the contamination will be diluted in the ocean, the longer this continues, the more radioactive particles will be released and the greater the impact on the ocean," said Chief Cabinet Secretary Yukio Edano. "We are strongly urging TEPCO that they have to take immediate action to deal with this."

The operator said Monday it is ordering fencing that is typically used to contain oil spills. The screens are not designed to trap radioactivity but might curtail the flow of water and thus reduce the spread of contamination, said TEPCO manager Teruaki Kobayashi. It was not clear when they would arrive.

Before restoring the cooling system, workers must rid the plant of the pools of radioactive water that have collected under each of the three troubled reactors' turbine buildings and have spilled into various trenches around the complex. TEPCO has proposed pumping it into tankers, barges and is now considering sending it to a storage facility on site.

Work on those problems continue to make progress, even as workers try to stop the latest leak, Nishiyama said.

"We have to apply stopgap measures to day-to-day problems, like the pit water leakage, but we are continuing on our effort to achieve the goal," he said.

Some of the reactors are made by General Electric, and the company's CEO met Sunday with TEPCO's chairman. Jeffrey Immelt told reporters Monday that more than 1,000 engineers from GE and its partner Hitachi are helping to analyze the problems at the plant.

Immelt also offered assistance in dealing with the electricity shortage brought on by damage to Dai-ichi and other power plants. Japan is expecting a shortfall of at least 10 million kilowatts come summer.

Gas turbines are on their way from the U.S. with both long- and short-term capabilities, Immelt said.

The Associated Press and NewsCore contributed to this report.