A dog, three sheep and a possum were electrocuted by a fallen powerline in Hawke's Bay, sparking a major emergency response.

Hamish Pollock, a 17-year-old shepherd at Landcorp's Paeroa Station, was rounding up a mob of rams on Saturday when he spotted three sheep lying in the boggy paddock with gas rising around them.

His dog Grace moved in to inspect them.

"She was a huntaway, so she was always barking. A few barks went higher and she just dropped and went rigid, which is a bit gutting.


"She dropped so quick I knew something was going on, I wasn't too keen to go down there."

As he moved closer along the bank above the dead animals a "pretty strong rotten smell" hit him.

Only one month into his first job, Mr Pollock could not make sense of the situation.

"I just thought, they haven't trained me for this".

Edendale Station manager John Speakman said when he arrived gas was still rising and the smell still strong.

"It was in line with the wires and I looked up, but it really didn't look like anything was down," he said.

"So because of a combination of circumstances and Hamish's description of the dog dying, I rang 111. Looking back it was an overreaction but at the time I thought it was the safest thing to do."

Mr Pollock was taken to hospital as a precaution and Central Hawke's Bay Council closed a nearby road.

Yesterday morning an emergency response team descended on the farm, including a Hazmat command vehicle.

"The firemen got out the binoculars and really studied the line ... and picked it up," Mr Speakman said.

"It was calm and clear, you don't expect power lines to come down in weather like that," Mr Pollock said.

Federated Farmers Hawke's Bay and national president Bruce Wills said the incident was "quite bizarre".

"It's a once-in-a-blue-moon event, especially on a fine day."

Mr Pollock was looking for a new working dog but he didn't think he would find one quite like Grace. "She probably saved my life," he said.