DNA tests have failed to identify a suspected murder victim whose bones were found in two black bin bags dumped in a river.
The bags were spotted beside a submerged supermarket trolley by a member of the public on Thursday afternoon in the River Stour in Sudbury, Suffolk.
Officers have so far refused to speculate on the age or sex of the remains and how long they may have been in the river, but it has been confirmed that the remains came from one person.
A post-mortem on the remains by a Home Office pathologist has been unable to determine how the person died.
Police confirmed on Sunday that they were also looking at the possibility that the bags may have been carried to the scene.
The passer-by who spotted the bags alerted a ranger from the Sudbury Common Lands Charity which manages the nearby water meadows.
The ranger fished the bags out and carried them 200 yards to an area beside the Roman Catholic church of Our Lady and St John the Evangelist.
He called police when he realised what was in them and a murder inquiry was launched on Friday after it was confirmed that the remains were human.
One theory is that the trolley may have been used to carry the bags down a path beside the river which overlooks water meadows between two foot bridges.
A Suffolk Police statement said: "A Home Office post-mortem examination of the remains was completed this morning (Sunday), but at this time it has not been possible to establish any form of identification or cause of death and further tests are now required. This will be a lengthy process."
Temporary Detective Superintendent Mike Brown, the Senior Investigating Officer, said: "This initial examination has unfortunately not been able to move us any further forward at this stage.
"The remains will now be subject to further specialist forensic tests which we hope will provide us with more information.
"This process will take time, so it may be a little while until we are able to provide any further significant updates.
"At the forefront of all of our minds is that this was a person - somebody's child, parent, partner or sibling - and at all times the bones will be treated with the utmost respect and dignity as the tests are completed.
"I would appeal to anyone who believes they have information about this discovery to contact us without delay.
"This includes anyone who believes they may know who deposited the remains, or anyone who saw someone carrying two black bin bags towards the river over the past week.
"We understand this discovery will have shocked and alarmed many people, but as stated before this is an incredibly rare occurrence and we do not believe there is any wider threat to anyone or cause for concern.
"Officers will remain at the scene over the coming days and extra patrols are taking place to provide reassurance.
"Finally, I just want to say thank you to all the local residents who have so far assisted us with this investigation, by either providing us with information, or simply for their patience as we conduct our enquiries."
The area around the river remained cordoned off on Sunday while divers from the Metropolitan Police Marine Policing Unit searched the water and forensic officers searched the riverbank and nearby area for clues.
Local residents have speculated that the black bags were not in the water for long as the river is well maintained and any rubbish is quickly cleared up.
Dog walker Barry Rock, 54, said he saw a trolley left beside a parking place on Wednesday evening just 100 yards from where the bags were found.
Mr Rock said he believed the trolley he had seen may have been used to carry the human remains before being thrown in the water.
He said: "It [the trolley] looked quite new and did not appear to have been in the water."
One local resident said: "My neighbour was walking with her daughters on the other side of the river at around 11am on Thursday.
"They saw a dumped shopping trolley and there was a man who was acting suspiciously. She said he kept looking at them and the trolley."
A woman whose home overlooks the area where the bags were left by the ranger said: "One of the officers told me words to the effect that I should not look out of my upstairs window because I might see something unpleasant.
"They later put up a tent on the spot, but they would not tell me what was going on. We have never had anything like this happen before."
Another resident who asked not to be named said: "I walked past the spot where the bags were found at about 1pm on Thursday and saw nothing suspicious or odd.
"There were just three girls aged about 13 messing about in a boat. It was an innocent scene, but it is rather chilling to think of it now.
"The river is very well kept and anything that is thrown in is quickly pulled out. That's why I think the bags could not have been in there for very long.
"This is the weirdest thing that has happened in the 20 years that I have lived here."
Detectives are also urging motorists who may have visited the area to review any recent dash cam footage they have to see if they captured anything of significance.
