Some Japanese plant workers, including former employees who are now miles away from the damaged nuclear reactors at the Fukushima Daiichi plant, say they are concerned about the health of their colleagues and the availability of equipment to keep them safe from the leaked radiation.
International nuclear experts believe that melted fuel in reactor No. 1 has caused a "localized criticality," which is a small, uncontrolled chain reaction that occasionally emits a burst of heat, radiation and a blue flash of light.
It is not a threat to the area at large, officials say, but could be deadly for workers.
One worker from inside the plant spoke anonymously about safety concerns such as not having enough radiation-detection devices available for workers.
The devices alert workers of too much exposure.
"Since the number of monitors is limited, only one or two devices are handed to each group," the worker said. "But sometimes you have to move away from that person and in that case you'll never know the level of your exposure."
He said workers are worried about their health.
"Some workers called it quits and just left for home," he said. "My gut feeling is that I want to get it over with and get out of here."
Officials at the Tokyo Electric Power Co., which operates the plant, said workers have had to work under harsh conditions.
They have since acknowledged the problem and promised more detection devices for their workers.
"They sleep on the floor, inside a conference room, or even in the hallway or in front of a bathroom," Kazuma Yokota, head of the Fukushima local office Japan's Nuclear and Industrial Safety Agency, said in a news conference.
"That's where they sleep, with only one blanket each to wrap themselves around."
Former plant workers living in a shelter just outside Tokyo, more than 100 miles away, told ABC News today that some people have been offered jobs to go back and help contain the leak.
"They're exchanging money with their lives," one worker said. "There may be people who will take the offer but it's not worth the risk."
Radioactivity in the water underneath the plant Thursday measured 10,000 times above the government standard. Earlier this week plutonium was also found in soil near the reactors.
Tokyo Electric Power said the company does not believe that any drinking water has been affected.
Radiation has also been found in tap water, milk and vegetables, which prompted the government to release a long list of banned food products from the region closest to the reactors.
Workers have been trying to restart the reactors' cooling systems since the 9.0-magnitude earthquake and tsunami on March 11.
Workers will soon have help from a U.S. company, as the world's largest concrete pumps are being shipped in from the United States.
They will first be used for spraying water from a greater distance than anything on site right now,and they might eventually be used to coat the reactors in cement and bury them for good.
Tokyo Electric Power said a remote-controlled robot being shipped from the the United States will also be used to check high radiation areas, according to the Associated Press.
The Associated Press contributed to this report.