An elite task force has been set up in Mauritius in a bid to catch those responsible for the brutal 2011 murder of Michaela McAreavey.
Prosecutor Satyajit Boolell said the investigation is ongoing and that those who killed her will "face justice".
Ms McAreavey (27) was strangled to death just 12 days after marrying John.
Nobody has ever been convicted of killing the popular teacher, who was the daughter of Tyrone GAA boss Mickey Harte.
Mr McAreavey has now travelled to Mauritius with his sister Claire and Mark Harte, Michaela's eldest brother, to make a renewed appeal for information. They will hold a press conference at the Labourdonnais Waterfront Hotel in the capital Port Louis this morning.
The newlyweds were honeymooning on the Indian Ocean island when she was discovered dead at their luxury hotel.
"We can't say this case is closed," Mr Boolell told the BBC. "We want to find out who the culprits are.
"Those who have taken the life of this young woman will face justice.
"We are as determined, we are as concerned, as he [John] is. Any crime on our territory is a blot on our peaceful reputation."
Mr McAreavey met senior police officers yesterday and afterwards said the meeting was "short but positive".
"We've been updated on developments, on how progress is being made," he said.
"We're enthused by what we hear. We have communicated that we are very much involved in this process now.
"We'll be doing all we can to assist the Mauritian authorities to deliver justice for Michaela."
The family also met the country's prime minister, Pravind Jugnauth.