A mix of chemicals led to the closure of a section of State Highway 3 on Monday evening.
The section of road between the two roundabouts on Broadway, Stratford, was closed for about four hours and traffic was diverted.
Stratford Volunteer Fire Brigade deputy chief officer Kevan Old says Fire and Emergency New Zealand was called to the scene at 4.53pm that evening.
Police, a St John ambulance and crews from Stratford, Toko, Eltham, and New Plymouth volunteer fire brigades attended the call-out.
Kevan says the fire crews had to call Australia to work out how to deal with the chemical mix.