British detectives working on the Madeleine McCann case are still pursuing "critical" leads as the 10th anniversary of her disappearance approaches, a Scotland Yard chief has said.
Metropolitan police assistant commissioner Mark Rowley said there are "significant investigative avenues" that are of "great interest" to both the UK and Portuguese teams.
Madeleine vanished from the family's holiday apartment in Praia da Luz in Portugal on May 3rd, 2007 when she was three years old — with her mother Kate saying the 10th anniversary is a "horrible marker of time, stolen time".
Officers have sifted through some 40,000 documents and looked at more than 600 individuals since 2011 with Mr Rowley confirming that four people considered as possible suspects in 2013 have been ruled out.
Kate and her husband Gerry McCann, of Rothley, Leicestershire, have always vowed to never give up hope of finding their daughter.
Asked if police were any closer to solving the case than they were six years ago when the UK investigation was launched, Mr Rowley said: “I know we have a significant line of inquiry which is worth pursuing, and because it’s worth pursuing it could provide an answer, but until we’ve gone through it I won’t know whether we are going to get there or not.
“Ourselves and the Portuguese are doing a critical piece of work and we don’t want to spoil it by putting titbits of information out publicly.”
He described the possibility of a “burglary gone wrong” as a “sensible hypothesis” which has not been “entirely ruled out”.
The senior officer was asked about the theory of a sex predator being responsible for Madeleine’s disappearance.
Mr Rowley said: “That’s been one key line of inquiry. The reality is in the modern world in any urban area if you cast your net widely you will find a whole pattern of offences.
“You will find sex offenders who live nearby. And those coincidences need to be sifted out, what’s a coincidence and what may be linked to the investigation that you are currently doing.
“Offences which may be linked have to be looked at and either ruled in or ruled out.”
Mr Rowley said there was still a “lot unknown” in the case, adding: “All the different hypotheses have to remain open.”
Meanwhile, police working on the case continue to receive information on a daily basis.
Mr Rowley said: “Thousands of pieces of information have come forward, some useful, some not, but amongst that have been some nuggets that have thrown some extra light on the original material that came from the time.
“That’s one of the things that’s helped us make progress and have some critical lines of inquiry we want to pursue today.”
Mr Rowley said there was no “definitive evidence” as to whether Madeleine is alive or dead.
He added: “That’s why we describe it as a missing person inquiry. We understand why, after this many years, people will be pessimistic, but it’s important we keep an open mind.”
Meanwhile, in a message posted on the Official Find Madeleine Campaign Facebook page Mrs McCann said they "couldn't even begin to consider anything in terms of years" when their daughter first disappeared.
She wrote: “Ten years — there’s no easy way to say it, describe it, accept it. And now here we are ... Madeleine, our Madeleine — 10 years.
“Most days are similar to the rest — another day. May 3rd, 2017 — another day. But 10 years — a horrible marker of time, stolen time.”