Tokyo: A Japanese state-run nuclear fuel laboratory near Tokyo has detected a radiation leak in its plutonium handling facility, but no workers were exposed.

The Japan Atomic Energy Agency said Wednesday a radiation alarm went off after nine workers changed plastic covers on two canisters containing a mixture of plutonium and uranium and removed them from a sealed compartment.

The agency said the workers, each wearing a mask, escaped radiation exposure after running into another room. No leak was detected outside the facility, which ended fuel production in 2001 and is being decommissioned.

The cause of the leak is under investigation. The agency suggested possible damage to the plastic covers.

A bag of plutonium broke during an inspection at another facility operated by the agency in 2017, contaminating five workers.