A GARDA investigation into a fire at a communications mast in Hollyhill is underway.
The emergency services were called after 11pm last night and extinguished the fire.
It is believed it was started deliberately and sources in the area told The Echo that in recent weeks, posters had been placed at the mast, in Ardcullen, and another one on Harbour View Road, containing opposition to 5G roll-out.
The incident follows two fires at a mast in Letterkenny in Donegal in recent weeks.
The investigation into those fires was probing whether they were related to conspiracy theories about a link between 5G and Covid-19.
However, the masts at Ardcullen and Harbour View Road, which were put in place late last year, are not for 5G.
Cork City Council, in a reply to a question posed by Fianna Fáil councillor Tony Fitzgerald, outlined last December that the masts were put in place to boost mobile phone coverage because the area was a mobile phone blackspot.
Mr Fitzgerald said: “I would be very concerned about any lighting of fires around any electrical equipment and the possible consequences to the public are huge.”
He urged people with information about the incident to contact gardaí.
Local resident, Sinn Féin councillor Mick Nugent, was alerted to the incident by a neighbour.
He said fire personnel had the situation under control quickly.
Meanwhile, Twitter has confirmed that posts encouraging people to take action against 5G masts will be removed as part of wider efforts to double down on dangerous "unverified claims".
The social network said it has broadened its approach, focusing on accounts inciting the public to engage in harmful activity which "could lead to the destruction or damage of critical 5G infrastructure, or could lead to widespread panic, social unrest, or large-scale disorder".
Though Twitter is prioritising such content, the company said it will not remove every tweet that "contains incomplete or disputed information" about coronavirus.
It comes amid a spate of mast vandalism attacks across the globe, driven by unproven conspiracy theories linking 5G to coronavirus shared on social media.
