Police are investigating after fires at two cell tower sites in the south Auckland suburb of Manurewa last night.

The police were called at 10.55pm to a fire at a lamp post cell tower on Blanes Rd in Weymouth. Around 11pm they were called to a fire at a power box, also at the site of a cell tower, on nearby Palmers Rd in Clendon around 11pm.

A police spokeswoman said inquiries were underway into the circumstances around both incidents.

There have been at least 16 suspicious attacks or fires at cell towers around the country in the past six weeks, as conspiracy theorists link the Covid-19 pandemic to the rollout of 5G wireless technology.

5G, or fifth-generation wireless technology, has been billed as ultra fast fibre broadband in your pocket. Among other improvements it's set to drastically speed up downloads and uploads via mobile.

It's being rolled out across New Zealand, and some new cell towers are being built and others upgraded to provide the technology.

But protesters falsely believe the coronavirus outbreak has been caused by 5G mobile network upgrades.

There have been at least 16 suspicious fires at cell tower sites in the past six weeks. Anti-5G protesters have also damaged networks in other countries.

A video of an earlier attack in Manurewa included anti-5G statements. A 37-year-old man has been charged over that arson attack and is next due to appear before the Manukau District Court on May 28.

Telecommunications companies have warned a spate of attacks on cell towers could mean internet is interrupted and calls to emergency services may not go through.

The Prime Minister's chief science adviser, Professor Juliet Gerrard, has reviewed multiple pieces of research and found no evidence of any adverse effects arising from 5G.

PM Jacinda Ardern has also said the claims tying 5G to Covid-19 are "totally false".

Fire and Emergency NZ shift manager Paul Radden said he understood one of last night's fires was significant and one was minor. One fire truck had been sent to each blaze.

The owner or owners of the cell towers had also been contacted, but Radden was unsure who they belonged to.