Police say that 15 witnesses have come forward following the murder of a man in Derry at the weekend.
56 year-old Christopher McGaughey was stabbed to death at Hollymount Park in the Gobnascale area of the city at about 1am on Sunday moring.
A woman also suffered minor injuries in the attack.
Police have been given an extra 36 hours to question a 31-year-old man, who was arrested on Sunday.
Detectives have already taken statements from 13 people and CCTV footage is being examined.