A man whose bones were found in two bin bags in a river died between 2008 and 2012, police have revealed a year after their discovery.
The remains were found in the River Stour in Sudbury, Suffolk, on 27 August 2020, sparking a murder inquiry.
Tests have now revealed the approximate year of death and that the man was in his late 50s to early 60s.
Suffolk Police's Assistant Chief Constable Eamonn Bridger urged anyone with information "to come forward".
ACC Bridger said the discovery, near Croft Bridge, had been the start of an "extremely complex murder inquiry".
"We said this would be a long and methodical process and it has proven to be just so, especially due to the type of specialist forensic testing that has been - and continues to be - taking place," he said.
"Many of the results that have come back then need to be subject to further tests and so we still have a distance to go."
Working with the National Crime Agency, Suffolk Police said nearly 1,150 statements and reports had been taken.
Officers said the victim's identity remained a mystery, despite them combing through 230 missing people records and looking at DNA databases in the UK and abroad.
Previous tests revealed the remains were of a man of "athletic or muscular build" but no cause of death has been established.
ACC Bridger said anyone with concerns over a male relative, friend or colleague, in his late 50s to early 60s, and not seen since the 2008-2012 period, should contact police.
He added they also wanted to hear from anyone who noticed someone acting suspiciously, or having a sudden change in their behaviour, in the days and weeks before the discovery.
A 26-year-old man, from Sudbury, arrested in May in connection with the inquiry was questioned before being released under investigation.