A threat against the head of Northern Ireland's biggest construction companies could harm the local economy, the First and Deputy First Ministers have warned.
The appeal comes after a bullet was sent to Kevin Lagan, chief executive of the Lagan Group.
It was posted to his Belfast office and was accompanied by a note that referred to a possible business deal with a firm formerly owned by the bankrupt billionaire, Sean Quinn. The note read: "Quinn... is this what you want".
In a joint statement, Peter Robinson and Martin McGuinness said: "We condemn the actions of those who posted a bullet to the Lagan Group. These actions do not help anyone and do not help local economic growth. The perpetrators of this act should be brought to justice. We encourage anyone with information to give it to the police."
The PSNI has launched an investigation into the threat.
Mr Lagan said he would not be intimidated and added: "The people behind this crude, intimidatory tactic clearly aren't interested in protecting jobs, but we will not be swayed from our determination to complete our discussions successfully."
The Quinn Group, which was previously owned by Fermanagh businessman Sean Quinn, was taken over by a consortium of banks in April 2011. There have been a number of attacks on Quinn Group property since new management took over the company in 2012.
Lagan Cement Group recently signed a memorandum of understanding with Quinn Building Products which could lead to a joint venture combining cement and building products businesses based in Ballyconnell, Derrylin, Kinnegad, Belfast, Cork and Benelux.
Both firms employ about 570 people and if the joint venture goes ahead it will be the second-largest cement supplier in Ireland.