A gas leak at Intel’s Chandler, Arizona, manufacturing plant sent a dozen people to the hospital over the weekend. At least 43 people became ill when a gas identified as nitrogen triflouride leaked from a single manufacturing tool in the company’s silicon wafer fabrication facility according to an Intel spokesperson.

Some 75 firefighters were called to the scene early Saturday after one worker complained of difficulty breathing. It was around this time that others began experiencing symptoms as well. 12 individuals were taken to local area hospitals to be treated for conditions including difficulty breathing, nausea, eye and skin irritation, said fire department spokesperson Tom Dwiggins.

The company’s second biggest manufacturing plant, home to around 11,000 employees, was promptly evacuated, the fire department spokesperson said. The leak occurred in a utility space that managed gasses and exhaust systems, we’re told. The tool responsible for the leak has since been taken out of commission and operations at the plant are back to normal.

As such, there’s no longer any outgoing danger nor was there ever any threat to nearby neighborhoods. The air inside and outside the structure was monitored and in all cases, the results came back clean.

The plant is home to two high-volume semiconductor manufacturing facilities. Intel is currently in the process of building a third facility on the campus which is scheduled to open later this year.

The cause of the leak is still under investigation as of writing.