A discovery of phosphorus at a Dunedin property led to emergency services drenching the material with a water cannon from a bucket lift.
A Fire and Emergency New Zealand spokeswoman said a "quantity of exposed phosphorus" had been found at a site in Rutherford St, Caversham, at 5.40pm yesterday.
The exposed material was dug up using an excavator and diluted with water.
Very little gas had come off the material.
A police spokeswoman said police were assisting with traffic control at the site.
David St was closed and there were cordons in place at Forbury Rd and Thorn St.
Residents nearby were advised to say indoors.