A New Zealand utility company that cut off power to the home of a woman on an electric oxygen pump, allegedly leading to her death, insisted Thursday it was not aware she depended on the machine.

The family of Folole Muliaga accused the company of calling them liars over the incident Tuesday, when the 44-year-old mother of four died two hours after a contractor, working for state-owned Mercury Energy, cut power to the house over an unpaid bill for 168.40 New Zealand dollars, or $123.

Muliaga's family claim she and her son told the technician she needed the oxygen machine to stay alive and invited him into the house to see it.

But Mercury Energy and its parent company, Mighty River Power, insisted Thursday they were never told that Muliaga depended on the electricity supply for her oxygen machine.

Mighty River's Chief Executive Doug Heffernan said the utility did nothing wrong when it cut the power shortly before the sick woman died.

He said there were different versions of the event, but that did not mean they were backing their own contractor.

"We have never said we are backing one story versus the other," he said. "It is not our job to make a judgment on what are the actual facts. That will come through the investigation."

Police and the local coroner have each launched investigations into the cause of the woman's death.

Meanwhile, the Counties-Manukau District Health Board, which issued Muliaga with the oxygen machine after her recent hospital admission, expressed surprise that she was so reliant on the machine that disconnection may have led to her death.

Chief medical officer Dr. Don Mackie told Radio New Zealand that Muliaga would not have been sent home if she needed the machine to stay alive.

"People who are on this are capable of breathing for themselves," Mackie said. "That is why we are surprised that she deteriorated and tragically died so soon after the support was withdrawn, and we need to understand more about that."

Mercury Energy defended its actions in a letter released Thursday.

"At no time was the issue of Mrs. Muliaga's medical condition or her reliance on medical equipment made known to the electrical contractor. He did note that she had a medical tube in her nose but this was not connected to any equipment," the letter said.

In any event, the contractor could not have been expected "to be able to make medical decisions," Heffernan told reporters.

The contracting firm that cut off the electricity to Muliaga's home, VirCom EMS, said it had been consulting lawyers, and that the staff member involved had been sent on leave, according to a report by the NewstalkZB radio network.

New Zealand's Gas and Electricity complaints commissioner, Judi Jones, said that while the circumstances of the case were still unclear, Mercury Energy could be held responsible for the contractor's actions.

Family spokesman Brenden Sheehan called Mercury Energy's denials "repulsive," and said the family felt the company was calling them liars for disputing its version of events.

Sheehan said that Muliaga's breathing grew worse in the two hours after the power was disconnected, and that she was "basically dead" when the ambulance arrived.