Embarrassed by bad publicity over Auckland's blackout, the government has begun investigating how the commercial heart of New Zealand's largest city could lose power.

Prime Minister Jenny Shipley, on a state visit to Japan, has tried to persuade business leaders and the Japanese public that downtown Auckland has almost returned to normal, telling them only one square mile of downtown is still affected by power shortages.That area, however, encompasses the offices of the biggest companies doing business in New Zealand, as well as some 5,000 apartment-dwellers.

One of the blacked-out buildings is the Japanese Consulate, and the Tokyo media greeted Shipley's arrival Tuesday with reports that Japanese diplomats in Auckland had been forced to move to a building with its own generator.

During an inspection of a new electric cable system being laid from the suburbs into downtown, Energy Minister Max Bradford announced the government will begin a probe of the power crisis after the utility company Mercury Energy has restored full power.

The investigation is to focus on the technical causes of the power failure, Mercury Energy's bureaucracy and contingency planning.

Many Aucklanders suspect that Mercury Energy skimped on maintenance of the four power cables serving downtown, laying off half its work force the past few years to keep profits rising.

The four cables failed between Jan. 22 and Feb. 20. It is not known why they failed, and a commission of experts says it may take six months to a year to find out. Mercury Energy has suggested the cables broke down as a result of the heat, soil settling and huge power demand.

Meanwhile, Mercury Energy chairman Jim Macaulay tried to stave off a wave of lawsuits by small businesses claiming losses totaling hundreds of millions of dollars.

Mercury Energy's rescue package for struggling businesses will be worth tens of millions of dollars, he said.

Downtown Auckland, meanwhile, is mostly cut off from the normal electric power grid, getting much of its electricity from portable generators and a ship docked in the harbor.