Mercury balls have dropped from a shelf at Kawhia School, prompting a full scale response from the New Zealand Fire Service.

A hazardous materials unit with firefighters donning chemical splash suits is en route to the primary school in the remote seaside village south of Raglan.

Fire Northern Communications Centre shift manager Jaron Phillips said mercury was toxic but he was unclear if the school had been evacuated.

However, the alarm was raised after school finished, about 3.10pm.

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Phillips said the mercury balls were in an old dental clinic at the school which was being refurbished.

"The mercury has fallen from within the wall."

Kawhia Fire Brigade was currently securing the scene and awaiting arrival from fire appliances from Otorohanga and Hamilton including the Hazmat Unit.

Phillips said firefighters carry mercury spill kits in case of such emergencies.
"It doesn't happen often but it does happen."

Exposure to mercury can occur from breathing contaminated air and can result in mercury poisoning.

Symptoms include vision, hearing and speech impairment, disturbed sensation, and a lack of co-ordination.