It’s been almost a decade since British 3-year-old Madeleine McCann vanished from her family’s hotel room in Portugal — but authorities say the case is far from cold.
In a statement Tuesday from London’s Metropolitan Police, Assistant Commissioner Mark Rowley said a team of four detectives continues to work on “outstanding inquiries” in Madeleine’s disappearance, with aid from their Portuguese counterparts.
“I know we have a significant line of inquiry which is worth pursuing,” he said, according to a Press Association story also published Tuesday. “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.”
“We’ve got some critical lines of inquiry, those link to particular hypotheses, but I’m not going to discuss those because those are very much live investigation,” Rowley reportedly said.
He said there are “significant investigative avenues” that are of “great interest,” the Press Association reports.
“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,” Rowley said, according to the PA.
According to the police statement — released ahead of the official anniversary of Madeleine’s disappearance on May 3, 2007 — Rowley confirmed that four individuals previously declared as suspects in 2013 have been cleared, after interviews and a search in a wasteland area near the McCann family’s residence in Portugal.
“We don’t have evidence telling us if Madeleine is alive or dead,” Rowley said in the statement. “It is a missing person’s inquiry but as a team we are realistic about what we might be dealing with — especially as months turn to years.”
Madeleine was just over a week away from turning 4 when she went missing from the family’s rented vacation apartment in Praia da Luz, Portugal.
According to Madeleine’s parents, Gerry and Kate McCann, she had been left with her 2-year-old twin siblings in the unlocked, ground-floor rental while they dined at a tapas restaurant just 130 feet away.
While the case drew international headlines, Portuguese authorities initially ended their review of the investigation in 2008. Five years later, however, Scotland Yard opted to reopen and fully fund a new probe. Authorities have reviewed thousands of documents and hundreds of people.
Gerry and Kate — who were cleared as suspects in the disappearance — also addressed the tragic anniversary in a joint statement shared to the official website dedicated to finding their daughter.
“The two themes that seem most appropriate to me as we reach this 10 year mark are perseverance and gratitude: We will go on, try our hardest, never give up and make the best of the life we have,” the parents said.
The family asked for reporters with renewed interest in the case to have a “conscience” and asserted, “We could spend all our time and energy trying to defend ourselves by correcting inaccuracies and lies, but then we would have no strength left to look for Madeleine, look after our other children and to live our life.”
In their statement, the parents also shared their gratitude for “so many kind and decent people over the last decade.”
“There have been many challenges and low points along the way but the warmth, encouragement and positivity we have experienced from the ‘quiet majority’ has undoubtedly sustained us and maintained our faith in human goodness,” they said.
“And while that is there, there will always be hope.”
This article originally appeared on PEOPLE.