Six workers of Japan's crippled Fukushima nuclear power plant have been directly exposed to leaking radioactive water. The Tokyo Electric Power Co (TEPCO), the plant's operator, on Wednesday said the unfortunate accident occurred due to carelessness when one of the workers detached a pipe connected to a water treatment system at the site.

Health analysts fear for the health of the six personnel. TEPCO said the exposure to the radioactive water was minimal.

"The water did not come into contact with their faces, so there is a little possibility that the workers ingested any of the water," ABC News quoted an unidentified TEPCO spokeswoman as saying.

The accident initially contaminated four of the cleanup workers. The other two got contaminated when they arrived to help. All were wearing protective clothing, including face masks with filters, protective hazmat suits and raingear.

The accident leaked out a total of ten tonnes of highly contaminated radioactive water.

The leak was immediately stopped within an hour of the accident after five other workers were able to reconnect the detached pipe.

TEPCO said the leaked water, which the workers got exposed to, contained beta radiation levels of 34 million becquerels per litre. Strontium-90, an agent usually included in most beta radiation, has been linked to causing cancers such as leukemia.

"It is serious in that it was another problem caused by carelessness, but I do not believe it is a seriously troubling dosage," Shunichi Tanaka, chairman of Japan's Nuclear Regulation Authority, said.

However, Mr Tanaka believed the situation at the crippled nuclear power plant could be more than carelessness.

"Careless mistakes are often linked to (declining) morale."

"People usually don't make silly, careless mistakes when working in positive environment and motivated. The lack of it, I think, may be related to the recent problems."

Since being hit by a tsunami two years ago, the Fukushima nuclear power plant and its operator TEPCO have been hit by a series of safety scares officials continue efforts to repair extensive damage.