The directors of Quinn Industrial Holdings (QIH) have received a death threat.
It was delivered to the Irish News newspaper and said it was a "last warning" to the directors.
Quinn directors were told about it on Monday night by the Garda (Irish police).
The anonymous letter said "we could have killed Kevin very easily", in reference to the attack on company director Kevin Lunney last month.
Mr Lunney was abducted near his home in County Fermanagh and badly beaten - his leg was broken and he was slashed a number of times with a knife.
In a statement, a spokesperson for Quinn Industrial Holdings said: "Regrettably, continuing threats are no surprise to QIH.
"It is just proof positive that this issue will not be resolved until the paymaster behind it is brought to justice and law and order is restored to this peace-loving community."
The letter also threatened Cavan County Council staff or other contractors who remove posters erected as part of the campaign of intimidation against the directors.
It warned that they will be targeted if they remove the posters.
One of the five Quinn directors, John McCartin, told Irish broadcaster RTE that the most recent death threat shows that the "faction" behind it are "emboldened and are undeterred from their specific agenda".
A Garda spokesperson said they do not comment on specific developments in ongoing investigations.
However, they added that they "continue to work closely with the PSNI and the Board and Directors of Quinn Industrial Holdings (QIH) in relation to all matters currently under investigation".