The force, popularly known as Scotland Yard, has been given 3.5 million pounds (more than $5 million) for the investigation, the Daily Mirror reported. A source inside the police called the job "enormous."
Madeleine's parents, Kate and Gerry McCann, left their children asleep in their holiday apartment at a Portuguese resort while they ate dinner with friends at an outdoor restaurant within view of the windows. Madeleine, then 3, disappeared that evening.
A police task force with a veteran detective in charge is expected to travel to Portugal to question witnesses and investigators and to examine the files assembled by Leicestershire Police, who handled the British end of the investigation.
Much of the money will go for translation.
The McCanns have accused Portuguese police of mishandling the investigation. The couple appealed to Prime Minister David Cameron to reopen the case.