Northpower lines staff are working to restore power to hundreds of homes and businesses around Whangarei after an explosion at its 33,000kV station at Maungatapere.

Spokesman Steve MacMillan said the explosion happened at about 11.30am, immediately cutting power to thousands of homes and businesses in the Maungatapere, Poroti, Kioraroa Rd and Whangarei South areas, including part of the CBD.

Mr MacMillan said many of the cut off properties would have had power reinstated within minutes, but work was ongoing to get the rest reconnected as soon a possible. He said it was not known at this stage what caused the explosion.