Almost a decade after three-year-old Madeleine McCann vanished, London police are still following critical lines of inquiry but say they might never solve the case.
McCann disappeared from her bedroom on May 3, 2007 during a family holiday in Portugal, while her parents were dining with friends at a nearby restaurant in the resort of Praia da Luz.
Despite a massive international search and media coverage, her fate remains a mystery.
"Sadly investigations can never be 100 percent successful," said London Metropolitan Police Assistant Commissioner Mark Rowley. He said police had no definitive evidence as to whether Madeleine was alive or dead.
- New possible witness could solve Madeleine McCann case
- Thousands demand Madeleine McCann's parents take lie-detector test
Her parents, Kate and Gerry, said the 10-year anniversary was "a horrible marker of time, stolen time".
In the 10 years since Madeleine vanished, the media has suggested a host of explanations for her disappearance, ranging from a burglary gone wrong to abduction by slave traders.
Madeleine's parents were named as official suspects by Portuguese police four months after the disappearance but in 2008 were cleared.
The McCanns and friends who were with them on the night Madeleine went missing later won large payouts from newspapers over stories that they were involved. Another Briton was awarded £600,000 (NZ$1.1 million) in damages over false allegations he had abducted the girl.
"We are bracing ourselves for the next couple of weeks," the McCanns said. "It's likely to be stressful and painful and more so given the rehashing of old 'stories', misinformation, half-truths and downright lies which will be doing the rounds in the newspapers, social media and 'special edition' TV programmes."
The Portuguese closed their inquiry in 2008. London police launched a review of the case in 2011 after the McCanns wrote to then British Prime Minister David Cameron.
"Where we are today is with a much smaller team focused on a small number of remaining critical lines of inquiry that we think are significant," Rowley said.
"If we didn't think they were significant, we wouldn't be carrying on."