The Northern Ireland Assembly says it has launched an investigation after the Irish flag was flown over the parliament buildings in Stormont today.
The tricolour was flown over the buidings for around 10 minutes before it was seen and removed.
In a statement this evening the Assembly said the roof of the building is currently a building site which was under the control of outside contractors.
Unionist politicians have complained about the incident, with one MLA even reporting the matter to the police.
DUP North Down MLA Peter Weir told UTV: “Whatever the motivation behind this there must be a full explanation from the Assembly as to who had access to the flag poles and who was responsible for this action.
“If it was carried out by someone working for an outside contractor, then this surely would represent a breach of contract which should result in sanction.
“It would also place an onus on the company to take disciplinary action against those responsible.”