A company replacing power poles is believed to have severed a fibre cable, cutting landlines, internet and cellphone networks to much of the Far North.
The Chorus-owned cable was cut about 10.15am.
Spark customers in Te Kao, Kaingaroa, Kaitaia, Houhora, Whangaroa, Hokianga, Maungataniwha, Karikari, Mangonui and Taupo Bay are affected.
A spokeswoman said the fibre line also supplied other providers so people using other networks could be affected.
Chorus had dispatched a technician and hoped to have the cut fixed by 6pm.