The British girl vanished during a family vacation in Portugal shortly before her fourth birthday in May 2007. Her parents left her and her siblings in their hotel room and went to a restaurant, and she hasn't been seen since.
Her parents, Kate and Gerry McCann, and a local man were once named as suspects, but they have since been cleared.
Authorities released an image of what Madeleine would look like now at the age of 9.
Detective Chief Inspector Andy Redwood said he is leading a team of more than 30 police officers reviewing some 40,000 pieces of evidence gathered so far. The team has identified some 195 possible leads to be followed up on, he said.
Redwood said forensic evidence of the sequence of events around her disappearance shows there are moments when she could have been snatched by criminals. He said he had an "open mind" on who could have abducted her, but asked for the help of Portuguese authorities, who closed the case in 2008.
"We would like the case to be reopened; our case is clear," Redwood told reporters Wednesday. "I should stress quite clearly that the decision is in Portugal."
He acknowledged that police have to consider that McCann may be dead despite hopes that she is alive.
Kate and Gerry McCann have pressed to keep the case in the public eye, publishing a book and appearing on the "Oprah Winfrey Show."
The Associated Press contributed to this report.