Nitric acid dripping from an overhead pipe weakened a water line, causing it to burst inside a defunct plutonium processing plant, Hanford officials said Friday.

There was some radioactive contamination to the hands of a worker who unsuccessfully attempted to turn off the water.

The acid had been used to help process plutonium. The pipe was located directly above the steel water line that burst on Thursday, leaking as much as 1,000 gallons of water into the plant, Hanford spokesman John Britton said. Crews were still cleaning up water Friday afternoon and were expected to work into the weekend.

Britton says it wasn’t known how the hands of the worker were contaminated. The radioactive contamination was later scrubbed off his hands.

Officials’ primary concern was keeping the water inside the building so contamination isn’t washed outside, Britton said. No water had escaped by Friday afternoon.

They also are concerned the water will wash hazardous materials from contaminated areas of the plant to clean areas. The full impact of the leak will not be known until after crews are finished cleaning up, Britton said.

The leak was discovered at about 4:30 p.m. Thursday. The water shorted some wiring, tripping a fire alarm, forcing fire crews out of the building. Firefighters returned inside the building and turned the water off nearly three hours later.

During the three hours, water continued to leak down a stairwell and into the plutonium processing area, Britton said.

The plant is located near the Plutonium Reclamation Facility, a separate building where a chemical tank exploded in May.