Gardai are investigating a suspected arson attack at a mobile mast site in Letterkenny on Sunday night.
The attackers are suspected to be related to a spate of 5G conspiracy theories currently being circulated.
An Eir spokesman said that the masts are not related to 5G, but are upgrades to existing 4G infrastructure to improve indoor coverage at Letterkenny Hospital and the surrounding area.
Both fires were extinguished by Fire Services and no injuries were reported. Gardai say that no arrests have been made and that investigations are ongoing.
The incident comes after attacks on dozens of 5G masts in Britain, with conspiracy theories linking 5G to Covid-19 or other health hazards.
Last week, protestors threw onions at mobile engineers upgrading a 4G mobile site in Dublin’s Ballyfermot suburb. The work was being done by the telecoms contracting firm KTL.
Although no-one was injured, one of the engineers targeted was on a monopole, said the company’s chief operating officer, Peter Dwyer.
“It was quite dangerous,” said Mr Dwyer, who said that industry workers upgrading telecoms equipment are increasingly on the “receiving end” of violent behaviour.
The attacks come as communications networks come under pressure to maintain capacity and service quality during the lockdown.
Last week, the telecoms regulator greenlighted additional spectrum capacity for the mobile operators, to help vital services and people working from home.
However, conspiracy theorists claim that 5G damages health through radiation, with some attempting to link to the spread of Covid-19.
Some celebrities have repeated to their followers the debunked claims about 5G being linked to Covid-19.
Actor Woody Harrelson reposted to his two million Instagram followers a conspiracy theory that the coronavirus emerged from the same region of China as 5G research.
British singer MIA (real name Mathangi Arulpragasam) has repeatedly claiming to her 650,000 Twitter followers that 5G signals can impair a body's ability to fight Covid-19.
UK TV presenter Amanda Holden asked her 1.9 million Twitter followers to sign a petition against the rollout of 5G, partly based on the suspicion that 5G-related symptoms were similar to Covid-19 ones. She later deleted the tweet, with her manager claiming that it had been an accident.
Last week, the World Health Organisation felt forced into publishing an advisory notice specifying that "5G mobile networks do not spread Covid-19… Viruses cannot travel on radio waves."
In recent days, Facebook has moved to limit false 5G claims linking the technology to the coronavirus.
Other celebrities have condemned attacks on mobile masts but have also criticised media attempts to label all 5G health scare claims as false.
Earlier today, ITV presenter Eamonn Holmes claimed that the issue was not yet completely settled.
“I don’t accept the mainstream media immediately slapping that down as not true when they don’t know it’s not true,” he told millions of viewers on the programme today.
“No-one should attack or damage [equipment] … but it’s very easy to say it’s not true because it suits the state narrative.”
A number of county councils around Ireland have passed motions calling for a halt to 5G rollouts, based on what they describe as health concerns.
However, medical, regulatory and scientific bodies have overwhelmingly rejected the fringes activists’ claims.
"There is simply no evidence to support worrying about phones or masts when talking about cancer risk," according to a guide by the Irish Cancer Society on the 5G health question.
"The changes to frequency used by technology such as 5G mean that these signals cannot even penetrate the human body. We know of no fundamental biophysical or biochemical mechanism for these signals to interact with important cellular functions."
This is echoed by Ireland's telecoms regulator and the World Health Organisation, which says that while radio frequency radiation is "possibly carcinogenic", it is not as risky as alcohol or processed meat.
In new guidance note to veterinary professionals on the subject of COVID-19 and passive transfer to animals, the Veterinary Council of Ireland (VCI) have said that animals that have contact with confirmed or suspect human cases should quarantined and kept in isolation for 14 days