Japan's Atomic Energy Agency said on Wednesday that five workers were exposed to high levels of radiation at a nuclear facility in Ibaraki prefecture on Tuesday. 

The workers were transferred to hospital for emergency treatment following an accident at the Oarai Research and Development Center north of Tokyo

Their condition is not thought to be life-threatening. 

The agency said the male workers were conducting an equipment inspection when a bag containing highly radioactive nuclear fuel materials split. All the workers were wearing masks over their mouths and noses but could have still inhaled radioactive material. 

No radiation leaked outside the building. The cause of the incident is being investigated.