Nicola Payne, 18, of Coventry, disappeared while crossing wasteland near her parents' house on 14 December, 1991. Her body has never been found.
The new searches in Coombe Abbey Country Park have so far produced "nothing of relevance" but followed "credible evidence", police said.
Two men were cleared of murdering Ms Payne last year.
After the court case, West Midlands Police pledged to continue investigating her disappearance.
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The force said officers have been searching the woods for eight weeks with help from scientists and dogs trained to find bodies.
Ms Payne's family has been kept updated and supported by family liaison officers.
A lake at the 500-acre site was searched in April last year.
Det Ch Insp Martin Slevin said: "These searches come after we received credible evidence from an eye witness concerning the sighting of two men in this area on the day Nicola disappeared.
"West Midlands Police is as committed as ever to finding Nicola's remains. We promised her family following the acquittal of two men last year that we would continue to investigate this crime and bring those responsible for her abduction and murder to justice.
"We will endeavour to bring them the closure they deserve."
He said "many items" had been submitted for examination but although nothing of relevance had so far been found, searches would continue until they either eliminate the site from the investigation or do find something important.
Anyone with information was urged to contact police as they may hold the "piece of jigsaw we are seeking," he added.
Nigel Barwell and his brother-in-law, Thomas O'Reilly, both 51 and of Coventry at the time of the hearing, were found not guilty of murder by a unanimous jury at Birmingham Crown Court last November.
Investigators are searching woodland in the hunt for a young mother who went missing almost 25 years ago.