Five more people have been arrested as part of the investigation into the attempted murder of Paul McCauley in Derry five years ago.
Three houses were also searched in the city.
Three men and a woman were arrested in Derry this morning, and a fourth man was arrested in England.
The three men arrested in Derry are 22, 42 and 49, the woman is 40. They were detained in at houses in the Fountain Estate and Kilfennan. The man arrested in the Midlands area of England is 24. Three houses were also searched in Derry as part of an ongoing operation.
Paul Mc Cauley was attacked after a barbecue on Chapel Road on the Waterside on July 16th, 2006 in a sectarian attack which the Independent Monitoring Commission later said the attack was perpetrated by UDA elements. Mr Mc Cauley, who was 29 at the time of the attack, has never regained consciousness, and remains in a coma.
One man, Daryl Proctor, is serving a 12-year term for grievous bodily harm over the attack.
Police say the investigation remains "active and ongoing".