Fresh death threats have been made against a director of Mannok Holdings, the company formerly known as Quinn Industrial Holdings.
The director, who is not being identified for security reasons, is believed to have been warned by police of four separate threats on his life.
The threats were intercepted in recent weeks by the Police Service of Northern Ireland (PSNI) and were conveyed to the director as being "credible".
Gardaí and the PSNI have stepped up security measures around all of the directors of the rebranded company, and a small number of new posters alleging "sabotage" have reappeared in the Cavan-Fermanagh Border region in recent weeks.
Police on both sides of the Border have been running a wide-ranging investigation into a history of attacks and intimidation directed at the former Quinn Group and some of its executives that began after it was placed in receivership by banks.
When contacted, the PSNI said: "We do not discuss the security of individuals and no inference should be drawn from this. We never ignore anything which may put an individual at risk."
The investigation is running in tandem with a separate inquiry into the abduction and assault of Kevin Lunney, the chief operating officer, in September 2019.
The five directors of the company received a Garda information message shortly after the attack, warning them about a credible threat to their safety.
Officers from the Regional Armed Response Unit have been mounting 24-hour patrols close to the plants on the Cavan border.
Gardaí from local stations have also been deployed to maintain a high-visibility policing presence, security sources said.
The company changed its name from Quinn Industrial Holdings to Mannok last year.
The cement and manufacturing businesses have been synonymous with the Quinn name in the Border region for decades.
Seán Quinn lost control of his businesses in 2011 to the former Anglo Irish Bank over a €2.3bn debt. His old businesses were bought by US hedge funds and a local consortium, and kept the name of their founder.
In a separate incident, a local man who assaulted Mr Lunney and Darragh O'Reilly at a petrol station cafe was sentenced earlier this month to more than three years in jail for the attack.
Bernard McGovern, from Kinawley, Co Fermanagh, admitted the offences.
Cavan Circuit Court was told McGovern punched Mr Lunney up to eight times in the face, leaving him with a broken nose and swollen eye.
He threw a cup of hot tea in chief financial officer Mr O'Reilly's face.
The judge described the attack as "callous and premeditated" and said McGovern had been motivated by a desire to avenge a grievance.
The court was told McGovern had no involvement in subsequent events in September 2019, when Mr Lunney was abducted and tortured.