There have been more than a dozen recent incidents of serious vandalism connected to businesses once owned by Fermanagh tycoon Sean Quinn.
The incidents date from around the time Anglo Irish Bank took control of much of Mr Quinn's empire, the BBC has learned.
The vandalism has caused hundreds of thousands of pounds in damage.
In the most recent attack, a cement factory near Derrylin was targeted and about £250,000 of damage caused.
Vans, a lorry and other construction vehicles were destroyed in the incident at the weekend.
Three electricity poles near Kinawley in County Fermanagh were also cut down.
There have been 14 similar incidents in the past three months. NIE said someone could be killed if the vandalism continues.
Police have said they have increased patrols in the area following the incidents, with officers being drafted in from outside County Fermanagh.
Sinn Fein MLA Phil Flanagan condemned the attacks and said they were "only adding to the continuing threat over the existing jobs within the Quinn Group".
Mr Quinn said those responsible were not acting in his name and called for them to cease.
Police Service of Northern Ireland Chief Inspector Sue Steen said Mr Quinn had made these comments to her at a recent meeting.
She said he had told her the Quinn Group was "something he had worked very hard to develop over a number of years" and he did not want to see it "destroyed".
Mr Quinn was stripped of control of his business empire in April and owes Irish banks billions of pounds.
In April, he conceded that he had made mistakes sinking millions into Irish bank shares, but said such mistakes should not result in a life sentence.
Mr Quinn and his family are now engaged in a complicated legal battle with Anglo Irish Bank which is owed 2.8bn euros (£2.4bn).
The bank claims the Quinns are attempting to move property assets into new firms which would cause it to lose security over significant sums of money.
The Quinns have denied the bank's allegations.
The legal proceedings have stretched from Ireland to Russia, Sweden and Cyprus.