Fukushima 50 Stay Behind to Prevent Nuclear Meltdown

They are known as the Fukushima 50, the workers who stayed behind at the crippled Fukushima Dai-ichi nuclear plant in order to prevent a meltdown in Japan.

Between 50 and 70 plant engineers -- who have not been identified and are being hailed as heroes -- continue to work around the clock in dangerous conditions, as hundreds of thousands have evacuated the area, fearing a meltdown.

Two of the workers are missing after an explosion and fire at the Unit 4 reactor, according to the Sydney Morning Herald. Workers have since resumed operations, Reuters reports.

"The longer they stay, the more dangerous it becomes for them," Margaret Harding of the American Nuclear Society told CBS News.

The engineers are trying to cool nuclear reactors with seawater, while trying to avoid fires and explosions.

"You are the only ones who can resolve a crisis. Retreat is unthinkable," Japanese Prime Minister Naota Kan told them, the Financial Times reported.

The workers have exposed themselves to high doses of radiation, which could cause cancer.

"These workers, in a few hours, are getting fairly high doses I would say by contemporary standards for worker protection, and that's likely to pose some risks down the line," David Richardson, a professor of epidemiology at the University of North Carolina, told the BBC. He added that the radiation the Fukushima 50 would receive in an hour is the same amount a U.S. nuclear worker would be exposed to over an entire career.

Last Friday's magnitude 9 earthquake and subsequent tsunami have left 11,000 dead or missing.