A portion of a main road in the south Auckland suburb of Penrose has been shut off after a chemical spill in the area.
Emergency services were called to the scene at about 6:50pm after a suspected carbide spill, Fire Service shift manager Paul Radden said.
"Upon getting wet, carbide can turn into a very flammable acetylene-type substance," Mr Radden explained.
The chemical spill has caused the closure of a large portion of Great South Rd (Tim Raethel / Newshub)
Seven crews are currently at the scene, including a number of specialist hazardous material units.
The severity of the spill is not yet known, but police confirmed that Great South Rd has been closed between South Eastern Highway and Sylvia Park Rd as a result of the incident.
Fire and police personnel collaborated to put the cordons in place, an operation Mr Radden described as "quite major".
Assistant area commander Roger Callister said the call was to a chemical processor that had malfunctioned.
"Due to a little failure in the cooling water system, the processor's making acetylene gas used in industries - and acetylene is quite explosive," he said.
"The shutdown process was brought about due to the cooling water escaping from the generator. We've got calcium carbide that is now sort of on the hot plate, with a little bit of water in it - which is a reactant.
"The problem with the acetylene is that, if it escapes, we have an explosive environment."
Mr Callister said the Fire Service had also cordoned off the area and evacuated the adjacent premises.
"That helps us reduce any ignition sources, and if gas did ignite, it keeps them safe from that explosion as well."