North Belfast loyalist leader Mark Haddock was arrested in jail today for questioning over four murders during the Troubles.
Specialist officers from the police's Historic Enquiries Team will be investigating Haddock in the hope of gathering fresh information on the murders during the 1990s.
The first killing dates back to January 17, 1993, when Catholic taxi driver Sharon McKenna was gunned down in north Belfast.
The 27-year-old, from Newtonabbey, was cooking dinner at the home of an older family friend when a masked gunman entered the house and shot Ms McKenna twice before escaping in a hijacked car.
Builder Gary Convie, 24, and electrical contractor Eamon Fox, 44, were eating lunch in a car parked beside a building site in Belfast's Tiger Bay area on May 17, 1994 when a gunman opened fire from a nearby playground.
The men, both Catholics, were killed in the attack. Fox's brother-in-law, who was in the back seat of the car, managed to escape uninjured.
The fourth murder over which Haddock will be quizzed is that of 39-year-old Protestant John Harbinson. The victim was beaten to death on May 18, 1997 by a UVF gang in Mount Vernon, north Belfast.
The 40-year-old from the Mount Vernon estate has been taken to Antrim Serious crime suite to be quizzed over the killings by members of the police specialist Historic Enquiries Unit (HET).
The senior UVF figure is currently serving a ten-year sentence in Maghaberry prison for attacking a club doorman.
Earlier this year Haddock was charged with the murder of rival loyalist - UDA leader Tommy English - in 2000.
Along with the murder of 40-year-old English, the four shootings were among 10 murders linked to Haddock's notorious UVF gang by a Police Ombudsman's report on alleged collusion between loyalists in north Belfast and security forces.
Haddock worked as an informant for the Royal Ulster Constabulary's Special Branch during the Troubles.
The probe by former Ombudsman Nuala O'Loan was triggered on the back of a complaint by Raymond McCord snr, the father of a UVF victim Raymond McCord jnr, who had claimed no one had been prosecuted for his son's killing in order to protect Haddock.
The HET, which was tasked to investigate the claims, has now arrested 16 men in connection with the killings. Eleven have been charged and four are subject to reports by prosecutors.
Haddock, who was taken from his cell in the high security prison near Lisburn, is also being questioned about a number of assaults and a shooting incident.