Christmas came and went, and despite the prediction of private detective hired by Kate and Gerry McCann that their daughter Madeleine would be found, the mystery of what happened to the 4-year-old continues.

Francisco Marco was hired by the couple to help find their daughter, who disappeared May 3 from a vacation apartment in Portugal.

"I cannot say who she is with because we are putting together conclusive proof we can present to the authorities so they can proceed with their arrests," Marco told the Spanish newspaper Metro on Dec. 13.

He had promised to find Madeleine by Christmas Day.

Click here to read Dec. 13 story on Madeleine's disappearance

Marco heads up the Barcelona-based Metodo 3, which has been working for the McCanns since September, the Daily Mail reported. Metodo 3 has been criticized by Portuguese police as "small fry" and "irrelevant," the newspaper reported.

"I have always said publicly Madeleine is alive," Marco reportedly told Metro. "I have to believe it 100 percent because I know how to look for living people, not dead ones. But I have no proof Madeleine is alive.

The McCanns, meanwhile, renewed their vow to never give up hope their daughter will one day be found.

"Rather than not leaving any stone unturned, it is that we never, never give up hope," Janet Kennedy, Kate McCann's aunt, told Sky News. "Eight months on, we have become even more determined and resolute and it (the message) becomes that we never, never give up."

"We are still very much thinking of Madeleine and a lot of people are staying the course with us," said Kennedy. "Kate and Gerry say that every day is a difficult day and we are just the same."

Click here to view the full report from Sky News.

Police are now focusing their investigation on a blue tennis bag allegedly taken from the family's apartment on the night Madeleine went missing, the Daily Mail reported.

The bag reportedly belonged to Gerry McCann, even though he told friends he didn't own a blue tennis bag or take any tennis equipment with him to Portugal, the Daily Mail reported.

Family spokesman Clarence Mitchell also denies Gerry McCann lost a bag during the vacation, according to the Daily Mail.

Click here to view the full report in the Daily Mail.