The hunt for missing Madeleine McCann extended to South America yesterday after a caller using a mobile phone in Argentina claimed to know the whereabouts of the four-year-old.

The "credible" call from a man was considered so potentially significant that the McCanns halted their search of Europe.

However, police sources played down the significance of the call, claiming it was just another among hundreds every week, all of which so far have been false leads.

Kate and Gerry McCann said yesterday that they would be staying in Portugal for the foreseeable future, five weeks after Madeleine was abducted from her bed in the Algarve resort of Praia da Luz.

They will make their final planned trip tomorrow night to Morocco, after a Norwegian woman in Marrakech said she was "99.9 per cent sure" that she had seen Madeleine with a man in a petrol station on May 9. The couple said they would then "take stock".

A family source said: "They don't put a specific timescale on it but they are prepared to live here until the end of the summer at the very earliest. They are now getting semi-regular meetings with Portuguese police and want to maintain that contact."