TOKYO (AP) — Two workers at the tsunami-wrecked Fukushima Daiichi nuclear power plant were hospitalized after accidentally getting sprayed with liquid laced with radioactive materials, officials said Thursday.

The incident occurred on Wednesday when a group of workers was cleaning the piping at the Advanced Liquid Processing System. The ALPS is a wastewater filtering facility that is key to the treatment of the radioactive wastewater that accumulates on the plant and its ongoing discharge into the sea.

Four workers were cleaning the piping when a drainage hose suddenly came off. They were splashed with the tainted liquid waste, which was not the wastewater running inside the system.

All four were wearing full face masks, and test results showed none of them had ingested radioactive particles. None have shown any health issues, according to plant operator Tokyo Electric Power Company Holdings, or TEPCO.

A fifth worker, who was also assigned to the cleaning work, was temporarily away when the accident occurred.

TEPCO began the controversial wastewater discharges on Aug. 24 from Fukushima Daiichi, which suffered triple meltdowns following the 2011 quake and tsunami. The discharges, which are expected to continue for decades, have been strongly opposed by fishing groups and neighboring countries, including China, which immediately banned imports of all Japanese seafood.

TEPCO has since completed the first two rounds of discharges as planned, and is preparing for a third, beginning in early November. Junichi Matsumoto, a TEPCO executive in charge of the treated waster discharge, told reporters that Wednesday’s accident would not affect discharge plans.

Following the accident, two of the four workers were able to rinse off the contamination to the levels that allowed them to leave the plant. The other two, who had the liquid soaked through their double-layer hazmat suits and underwear and could not sufficiently lower the radiation levels, had to be taken to a hospital for further decontamination and monitoring, TEPCO said.

One of the hospitalized workers, in his 20s, was found to have exposures on the whole body except for his face, while the other man, in his 40s, had exposures in the stomach area. Risks for them to get skin burns from the radiation exposure were extremely low, TEPCO said, quoting a doctor who had examined the two workers.