Cordon widened after corrosive gas cloud

An acid leak drama in Auckland this morning is coming to an end in a cloud of steam.

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Workers on the billion dollar Waterview tunnel project early this morning discovered a 1000-litre container of hydrochloric acid had been punctured, leaking its contents and creating an acidic cloud.

Police spokesman Noreen Hegarty said roads around the suburbs of Mt Albert and New Windsor were closed as the Fire Service tracked the cloud southwestward.

The blockades remained in place as workers dealt with the spill at the eastern end of the tunnel.

Pupils at the Christ the King School on Richardson Road were asked to remain indoors as the spill was treated with caustic soda.

Hegarty said the treatment would result in a cloud of steam visible over the area but it would be a low risk threat to health.

As a precaution, police widened the cordon area and advised people to stay indoors. Construction workers at the tunnel had been removed from the area.

Hegarty said a police staff member had suffered an allegic-type reaction to initial cloud, but no other people were hurt.

Fire Service spokesman Scott Osbourne said 15 fire engines and 60 staff were at the scene.

"We will be there for some time," he said.

Hydrochloric acid is a clear and colourless solution of hydrogen chloride in water.

It has many industrial uses in the chemical industry and is widely used in household products such as cleaning solutions.

In its concentrated form it can form acidic mists and can have a corrosive effect on human tissue.

The Waterview tunnel, when finished, will connect Auckland's southwestern and northwestern motorways to complete a loop around the city.

The Transport Agency confirmed the accident had occurred at their site and they would comment later today when they had investigated what happened.