The Indiana Occupational Safety and Health Administration plans to investigate an acid spill that injured nine workers on Friday at a Rolls-Royce aircraft-engine assembly plant near the Indianapolis International Airport.
IOSHA spokesman Bob Dittmer said the agency is likely to start the investigation Monday. It could take up to three months before official findings are released, he said.
The workers were injured when a tank of nitric acid exploded and filled the building with a cloud of corrosive vapor, officials said.
None of the workers suffered life-threatening injuries when the 250-gallon tank exploded about 1:30 p.m., Capt. Mike Pruitt of the Wayne Township Fire Department said. The explosion released a vapor cloud that left the workers with burns and breathing problems.
"Their main complaints were that they had inhaled it and they had some acid burns. It's a corrosive acid," he said.
Pruitt said eight workers were taken to local hospitals and released Friday night. The ninth person was treated at the scene.
The cause of the explosion — and how much acid was released — remains under investigation by Rolls-Royce and fire officials, Pruitt said. He said the injured workers will be interviewed to determine how the explosion may have occurred and what they were doing before the blast.
The plant, at 2355 S. Tibbs Ave., hasn't had any safety violations since 2011, according to IOSHA records, and those violations were minor and unrelated to acid storage or treatment.
The plant was evacuated immediately after the explosion, but the vapor later dissipated and Rolls-Royce staff members were allowed back inside.
Rolls-Royce spokesman Joel Reuter said the tank containing the acid exploded either as it was being moved or shortly after it had been moved by a device used to transport equipment inside the plant.
"We're still determining whether it was actually moving or what, but it was in some in type of transportation mode," he said.
Rolls-Royce canceled the plant's remaining Friday shifts, but Saturday's shifts were scheduled to proceed as planned.
He said the plant's workers assemble engines for military and commercial aircraft.
The National Institute for Occupational Safety and Health says nitric acid is corrosive and the vapor or mist form can irritate the eyes, nose, throat and skin. High concentrations of vapor can severely burn the eyes and skin.