A knife seized in the Nahid Al-Manea case has been ruled out but officers are still awaiting results from more than 2,000 items.
Forensic officers were called to Hawthorn Avenue in Colchester last Tuesday afternoon after a man discovered a knife in the road.
The scene was cordoned off and the knife was sent for tests.
Today DCI Steve Worron said: "I can confirm that the knife found in Hawthorn Avenue, Colchester, on Tuesday, June 24, has been ruled out of the investigation following forensic tests.
"I would like to thank the member of the public who told us about it and would urge anybody who does see anything suspicious to contact us immediately.
"People may be in their gardens over the weekend and if they see anything they may not have spotted before call our incident room on 01245 282103."
There are more than 100 detectives working to solve both Nahid's murder on the Salary Brook Trail on Tuesday, June 17, and to find the killer of James Attfield, who was attacked in Lower Castle Park in March.
In relation to the murder of Nahid Essex Police has
• Taken more than 200 statements from the public
• Carried out anniversary checks in the area of the Salary Brook Trail a week on from her murder and two weeks on
• Received 527 calls into the incident room
• Visited more than 600 properties as part of house to house enquiries
In total 367 search officers have worked over a 15 day period, working 12 hour shifts. There have been 30 search officers on duty at any one time.
These search teams have been supported by other agencies which have helped to clear trees and drain lakes. So far 450 metres of the Salary Brook Trail has been searched as well as 48 private gardens.
The force has also dredged 468 drains.
During the searches 2,100 exhibits have been seized and this number is expected to rise as our search of the Salary Brook Trail area continues over the weekend.
The investigations into the murders of Nahid Almanea and James Attfield are two of the largest carried out by Essex Police in last 10 years.
Mr Worron added: "Their family and friends have my commitment that Essex Police is doing everything possible to bring those responsible to justice."
Investigations into the murders of James Attfield and Nahid Al-Manea are costing about £100,000 a week.
Since the murder of Nahid, 31, in Greenstead on Tuesday, June 17, the two investigations combined cost £250,000 in the first 12 days.
More than 300 officers are working on the investigations to try and find the killer or killers including many from other forces.
The large scale investigations and public reassurance patrols will continue for the forseeable future as police do all they can to catch those responsible.
Nahid, who was living with her brother in Woodrow Way, was studying an English language course at Essex University.
She arrived in the UK six months ago and was working towards a PhD in life sciences when she was stabbed 16 times and killed on the Salary Brook Trail shortly before 10.40am.
James 'Jim' Attfield, 33, of East Bay, Colchester, was stabbed 102 times and found near Castle Park just before 6am on Saturday, March 29.
Four people are currently on bail in connection with the murder of father-of-five Jim.
Two people were arrested and released without charge in connection with the murder of Nahid.
Det Chief Supt Steve Worron said: "It is extremely unusual to have two knife related acts of such ferocity in quick succession.
“We have no witness who has seen the killer or killers commit these crimes.
“We are committed to making sure we get justice for James and Nahid, their families and the wider community of Colchester.”
2,000 exhibits have been sent for forensic tests during the ongoing search around the nature reserve.