Mr Quinn was found at farm buildings near the village of Oram

The 21-year-old died after being beaten by nine men wielding iron bars at a remote farm shed in County Monaghan on Saturday.

A senior PSNI detective has travelled to Castleblaney to liaise with garda officers.

Sinn Fein has denied claims by Paul Quinn's family that members of the IRA were responsible for his death.

First Minister Ian Paisley has asked the prime minister for his full support if it turns out the IRA were involved in the murder.

The DUP said IRA involvement "could collapse the political institutions" after Mr Quinn's family said the organisation had killed their son.

Sinn Fein's Gerry Adams has denied republicans were involved.

"Others may want to play politics with this dreadful murder. I don't and I won't," he said.

"There is no republican involvement whatsoever in this man's murder and all of us should be careful that we don't end up playing politics with what is a dreadful, criminal action."

However, speaking after talking to Gordon Brown, Mr Paisley said IRA involvement would have serious consequences.

"If this murder was the work of the Provisional IRA then very serious consequences will flow from that," he said.

"As a party we have made it clear that there will be no place in government for those associated with murder."

Earlier on Monday, former Sinn Fein politician Jim McAllister alleged Mr Quinn had been involved in recent rows with republicans.