A 1000-litre spill of nitric acid in the Christchurch suburb of Middleton has been contained.
A Fire and Emergency spokesperson said four crews and a command unit were called to Baigent Way off Lunns Road about 12.45pm.
St John Ambulance was at the scene and treated five people inhalation.
They said the spill had been contained by 3.30pm and crews were working to clean up the remainder of the spill by applying a neutralising agent.
Area Commander Mike Bowden said crews were still cleaning up the mess.
Bowden said the region's fire services had been stretched this week - particularly after four fires yesterday.
Southbound lanes on State Highway 73 between Blenheim Road and Lunns Road remained closed this afternoon.