Work at the No. 2 reactor at Japan's stricken Fukushima nuclear plant was halted today after radiation levels of 500 millisieverts were detected, Kyodo News agency reported.

The work suspension came after two workers at the plant were injured while toiling on power restoration, according to Reuters.

External power was reconnected to all six reactors at troubled Fukushima earlier today, bringing Japanese engineers one step closer to restarting the facility's desperately needed cooling systems.

However the continued leakage of radiation was proving a problem at the scene and much further beyond, with fears about continuing contamination of food and water.

To put the 500 millisieverts detected at No. 2 reactor into perspective, background radiation levels of around 1.5 millisieverts every year are normal and poses no harm, according to the Australian Cancer Council. Nuclear workers are allowed exposures up to 20 millisieverts annually.

"At 100 millisieverts exposure, there will be one additional cancer detected years later for each 100 people exposed," the Cancer Council said in a statement on its website, adding that the cancer risk due to radiation leaks at Fukushima was "minimal."

Despite reassurances from authorities, concerns about the potential fallout from the nuclear crisis following the March 11 earthquake and tsunami continued.

Earlier Wednesday, two prefectures affected by radiation leaks from the plant were instructed to stop shipping a range of farm products.

Japanese Prime Minister Naoto Kan issued orders for the shipments of green leaf vegetables and broccoli from Fukushima and untreated milk and parsley from Ibaraki to cease immediately.

The health ministry said radioactivity drastically exceeding legal limits had been found in 11 kinds of vegetable grown in Fukushima prefecture, AFP reported.

Radioactive caesium at 82,000 becquerels - 164 times the legal limit - was detected in one type of leaf vegetable, along with 15,000 becquerels of radioactive iodine, more than seven times the limit.

The ministry said that if people ate 100 grams (four ounces) a day of the vegetable for about 10 days, they would ingest half the amount of radiation typically received from the natural environment in a year.

Even if the short-term risk is limited for now, scientists pointing to the 1986 Chernobyl disaster warn that some radioactive particles concentrate as they travel up the food chain and stay in the environment for decades.

On Tuesday, the US Food and Drug Administration (FDA) announced it would temporarily halt the import of all milk, vegetable and fruit products coming from the four prefectures - Fukushima, Ibaraki, Tochigi and Gunma - thought to be affected by radiation.

The move, called an "import alert" amounts to a 180-day ban on imports and was authorized in "response to public fears about radiation from Japan's crippled Fukushima Daiichi nuclear plant," an FDA spokesperson said.

France urged the European Commission to impose "systematic controls for all fresh produce reaching Europe's borders" from Japan, while stressing that it was not calling for a total embargo on Japanese food products "at this stage."

Around Asia, many Japanese restaurants and shops are reporting a decline in business and governments have stepped up radiation checks on the country's goods. Tainted fava beans from Japan have already cropped up in Taiwan.