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 - may have been chasing a phantom.

Officials admitted Thursday that the woman might not actually exist. This was because DNA found at the crime scene and attributed to her was probably tainted.

New examinations showed the swabs used to collect the DNA were in all likelihood contaminated, said Ulrich Goll, justice minister in the state of Baden-Wuerttemberg, where police have been spearheading the hunt.

"Something like this should not have happened," said the minister, who defended the police and forensic experts responsible for collecting the samples. "They were not able to tell there was anything wrong with the swabs."

Police are now testing the swabs they use to collect evidence at crime scenes to see if they already contain DNA fragments.

The first genetic traces of the suspect, dubbed by the German media as "the woman without a face," 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)