Detectives are questioning three people, believed to be Lithuanian, about the murder of two men whose bodies were found in Warrenpoint, Co Down.
The victims are also understood to be from Lithuania but had been living in the North for some time.
The bodies were discovered in thick undergrowth on the Mound Road. Two men were arrested early yesterday after police raided a house three miles away in Sandy Street in Newry, Co Down. A third person was arrested yesterday evening. The house has been sealed off for forensic examination.
The victims, who were aged between 20 and 30, are believed to have lived there since December. They were last seen alive on Sunday night.
Detectives are investigating the possibility that the double murder was a result of an argument between illegal immigrants. They have brought in an interpreter to enable the arrested men to be questioned.
The Police Service of Northern Ireland is attempting to trace two cars which may be linked to the murders.
Officers are also carrying out searches in the Mayobridge area of Co Down where it is understood the victims had worked on mushroom farms.
The men's bodies were discovered on Wednesday. One was lying on top of the other. It is believed they were killed elsewhere, then moved to the Mound Road. They had been stabbed and badly beaten about the head and body with blunt instruments. They were naked from the waist down, and at least one had his throat slit.
One of the victims has been positively identified as a Lithuanian, while the second is also believed to be from the Baltic country.
Local farmers said the dead men were among a group of Lithuanians who had been working on mushroom farms in the Newry and Mayobridge areas.
One mushroom farmer, who has been questioned by detectives and who did not wish to be named, said: "They did odd jobs for us now and again. We didn't even know their names. They fell out among themselves. It is a horrific outcome."
It is believed there was some suspicious activity at the house in Sandy Street late on Sunday or early on Monday.
Neighbours said four Lithuanians had been living in the house, and more had been living in other houses nearby.
They had been quiet and were never violent, the neighbours said. Mr Billy Sinnerton, an honorary consul for Lithuania, described the double murder as shocking.
"I was in touch with the embassy and it has come as a great surprise to them," he said.
"They have been in touch with the PSNI and the detective superintendent who is handling the case. They are just waiting for more information."
Forensic scientists were yesterday continuing to search Mound Road, where the bodies were dumped. Detectives are awaiting the results of post-mortem examinations on the men.