A fourth man has been arrested in relation to the killing of dairy farm worker Justin McFarlane, who was found dead in his home near Oamaru last Wednesday.
A 22-year-old man was arrested on Monday night after police tracked him down on a public bus travelling north from Dunedin to Oamaru.
His arrest follows the arrest Sunday of a 23-year-old Oamaru man, and the earlier arrests of a 22-year-old and an 18-year-old.
Police made Monday night's arrest after receiving information the 22-year-old and his girlfriend could be on a bus.
The man was taken to Dunedin Central Police station for questioning and remanded in custody to appear in the Dunedin District Court on Tuesday.
Acting Detective Inspector Colin Blackie said a fifth person, a 52-year-old Oamaru woman, had been charged with being an accessory after the death.
As well, up to eight more people could be arrested for hampering the investigation or destroying evidence, Mr Blackie said.
"A second phase of this investigation ... is that those people that we've identified that have been less than helpful, we'll investigate the facts surrounding (them) and, if necessary, they'll be arrested and charged with their part in hindering the investigation."
The investigation was only about halfway through, he said.