Berlin - Police who spent 16 years looking for one of Germany's most wanted criminals - a mystery woman suspected of three murders and 40 robberies - admitted Friday they had been chasing a phantom.

The DNA found at the crime scenes and traced to her belonged to another woman who in all probability had nothing to do with the crimes, prosecutors in the southern town of Heilbronn said.

The woman was an employee at a packaging plant in Bavaria which handled the cotton swabs used by police to collect DNA samples, officials in the southern state of Baden-Wuerttemberg said.

Police admitted Thursday that the swabs were probably contaminated with the DNA of a person other than the "woman without a face" they had been looking for.

First indications that the swabs might have been tainted came earlier this month from Austria, where one of the crimes committed by the mystery woman allegedly took place.

Police then went to the packing firm in Bavaria where they took saliva probes of all employees. In this way they were able to trace the DNA of the tainted swabs to the female worker.

The first genetic traces of the suspect, also dubbed by the German media as "the phantom of Heilbronn" turned up at murder scene in May 1993.

Later DNA evidence linked her to the 2001 killing of a man aged 61 as well as the cold-blooded murder of a 22-year-old policewoman at a car park in the town of Heilbronn in April 2007.

Other finds included clothes left at a robbery scene in Austria and a syringe containing drugs that had blood on it identified as that of the suspect.

Police went on television in April 2005 with an appeal to the public for information, but no one ever came forward. There was also a reward of 300,000 euros (400,000 dollars) for evidence leading to her arrest. (dpa)