A security alert close to Saturday's big boxing event at Windsor Park may be linked to the Hutch-Kinahan feud, sources have said.
Police were called to a railway bridge in south Belfast following a bomb scare as 23,000 fight fans gathered ahead of the show, which featured Belfast boxers Carl Frampton and Paddy Barnes, as well as heavyweight Tyson Fury.
Police later confirmed it was a hoax.
Residents from the area were taken to Olympia Leisure Centre while ammunition technical officers examined the scene.
Areas around Great Northern Street and Northbrook Street were cordoned off for several hours.
A source said one of the main theories was that the disruption was connected to the Hutch-Kinahan feud, an ongoing gangland wrangle between two crime families in Dublin.
The PSNI would not comment on whether the alert was linked.
Chief superintendent Simon Walls said: "A device left in the Lower Windsor area was examined by ammunition technical officers and declared a hoax.
"Roads that were closed were quickly reopened.
"I want to thank residents for their patience while we worked to keep the community safe.
"I would urge anyone who may have witnessed any suspicious activity in the area, or anyone with information which could assist with our enquiries, to call us on 101."
The Kinahan-Hutch feud has been ongoing since 2015 with more than a dozen tit-for-tat murders being carried out by the factions.
The Hutch gang is led by Gerry Hutch and the Kinahan family by Christy Kinahan.
Many of the murders have taken place within Dublin's north inner city.
The first victim was Gary Hutch, shot dead in Spain three years ago.
He was a nephew of Gerry Hutch.
Hutch is a notorious Dublin criminal who goes by the nickname of 'The Monk'.
In February 2016 gunmen dressed in police SWAT team uniforms opened fire inside Dublin's Regency Hotel while a boxing weigh-in was taking place.
They killed 33-year-old David Byrne, who was believed to be a member of the Kinahan gang.
The latest victim was Derek Coakley Hutch, another nephew of the notoriouis Hutch.
He was gunned down in the Bridgeview halting site in Clondalkin in January.