10/09/2013 02:18 EDT | Updated 12/08/2013 05:12 EST

6 workers splashed with toxic water at Japan nuke plant as they remove wrong pipe

TOKYO - The operator of Japan's crippled nuclear power plant says six workers have been exposed to highly radioactive water that poured out of a treatment unit when they removed a wrong pipe.

Tokyo Electric Power Co. said Wednesday that exposure to the workers, who were wearing face masks and protective gear, is believed minor but still under investigation.

Tons of highly toxic water spilled out in the incident, covering the facility's entire floor, TEPCO said.

The mishap is the latest in a spate of recent leaks and problems caused by human error that have added to public criticism of TEPCO's handling of the crisis.

Last week, workers overfilled a tank without fully checking water levels, causing a leak, possibly to the sea.