Emergency generators have begun arriving in Gisborne to provide power for elder care facilities, and fuel and food outlets.

The city is expected to be without electricity until late tomorrow at least, after a plane crashed into high voltage lines this morning, leaving 20 thousand homes and businesses without electricity.

The two people on board the plane have died.

Civil Defence said some areas including the East Coast, north of Tolaga Bay and west of Gisborne have had power today thanks to generators in sub-stations, but these have just been turned off to conserve diesel.

Residents with no power have intermittent cell phone coverage.

Spark said four of its cell tower sites are down but five others are running on limited back-up battery power.

It's asking customers to conserve mobile phone battery life, and use Voice and SMS services rather than data.

Residents are being urged to check on neighbours and save water.

Eastland Network CEO Brent Stewart said hard-working specialist teams might be turning the lights back on sooner than initially thought.

"Probably tomorrow afternoon, if not evening, hopefully we can be sooner than that, but probably realistically that's the best prognosis at this time" he said.

Police have also announced they will have a heavy presence in Gisborne overnight with concerns of a possible increase in crime with the blackout.

More police staff are being rostered on and extra patrols will be conducted, especially in the CBD, to discourage looters and vandals.

Gisborne reporter Murray Robertson said police have reassured the public that they will be there for them all through the night.

"They'll be out there to keep a close eye on any likely spike in criminal activity" he said.