Some of the barrels had tipped over and spilt the oil on the ground.

A police spokeswoman said that police had contained the spill but it could have been dangerous to locals.

“The spill has now been contained but could have run into the upper Nihotupu Reservoir which had the potential to contaminate the water supply,” she said.

Piha resident Sarah Munro told the Herald that locals believe they were dumped sometime last night.

“We think it was last night because nobody had seen it before that.

“I went past at about 8.30 this morning and saw the sites where they dumped them.”

She added that others thought somebody had removed distinctive features from the drums that may have helped locate where they originated.

Piha, Karekare and Anawhata locals regularly call the council to have rubbish removed, but she said that this was an all time low.

“It’s a major problem dumping rubbish at Piha – there is often household rubbish, furniture and even cars.”