BRITISH detectives probing the Madeleine McCann disappearance in Portugal want to retest hairs after it was found previous DNA tests carried out during the original investigation were incomplete.

Police investigating the disappearance of Madeleine McCann want to DNA test hairs[AP]

Nearly 100 strands of hair tested during the original Madeleine McCann investigation were never DNA-matched, it emerged today.

Portuguese forensic experts analysed 444 hair strands they believed could hold the key to the youngster’s May 3 2007 disappearance.

They found 432 were human and 12 non-human. They were unable to DNA-match 98 of them and only obtained partial results from 19 of them, Portuguese daily Correio da Manha reported.

British detectives probing Madeleine McCann’s disappearance want to retest some of the hairs as well as curtains hanging in the Algarve apartment where she vanished.

Scotland Yard are expected to apply for permission in a sixth international letter of request to take the samples from a Portuguese lab so experts can look at them in the UK.

The fifth letter, understood to contain a request to reinterview three new suspects quizzed in the summer, has yet to be answered by new Madeleine McCann prosecutor Ines Sequeira.

A Met Police team led by DCI Andy Redwood announced their wish to look again at forensic material collected in the early days of the Madeleine McCann investigation during a visit to the university town of Coimbra earlier this month.

They met with the bosses of Portugal’s Institute of Legal Medicine and Forensic Sciences in Coimbra, two hours drive north of Lisbon, where most of the material, also said to include 25 blood and saliva samples, is held.

Institute president Francisco Brizida, said afterwards: “I have the certainty they went away very happy.”

“The tonic of the meeting was about the possibility of the tests on samples collected in 2007 being re-done.

“The British police wanted clarification on the examinations the institute had carried out during the early stages of the inquiry in the areas of genetics and biology.

“We talked about non-identified material that was collected in Madeleine’s apartment.

“I can’t say for sure new DNA tests that didn’t yield a conclusive result in 2007 could now yield an objective result.

“But technology nowadays allows us to go further than years ago in areas like genetic markers.

“Several possibilities are open. One could be that British police do the tests in Britain with British technology and another that the institute does them.

“But that’s an area in which the institute does not have the last word. There’s a situation of judicial cooperation and a new international letter of request would be necessary.