For seven days they have sustained themselves on hope and playing an active role in the search for their missing three-year-old daughter.

But last night the hunt for Madeleine McCann entered a bleak new phase when Portuguese police said the case was being wound down. However, they emphasised that they had not given up, and confirmed they were investigating clips of CCTV film and other leads from a large number of sources.

It as confirmed clips were taken. They were believed to include video from a petrol station of a car with a British number plate.

The police announcement, signals a probable end to intensive physical searches around the Algarve resort where Madeleine was abducted a week ago. Around 930 police officers have been involved in the search and some are likely to be reassigned.

Her family are hoping the investigation will now be focused more towards detective work - there are an estimated 350 leads to be followed up - but it leaves Madeleine's parents, Gerry and Kate, in limbo.

Last Thursday night they returned from dining with friends at a tapas bar opposite their holiday apartment in Praia da Luz to discover Madeleine, who will be four tomorrow, was gone.

They had left her sleeping with their two-year-old twins, Sean and Amelie. John McCann, her uncle in Glasgow, who arrived home from the Algarve earlier in the week, said that he would not be too concerned at the winding-down if it meant a switch in emphasis from physical searches to detective work.

"Searching the area around the resort has been a waste of time since the start," he said. "I was there on Monday, out searching for five hours on land which, from a logistical point of view, no-one would have gone to dump a child.

"I think they were just doing it because they thought they had to. Maybe they should be channelling their forces more towards detective work. As long as they are continuing to pursue the leads they are getting - we are depending on them to keep up the detective work."

Earlier yesterday the couple were driven to the Policia Judiciaria (PJ) headquarters in Portimao for more interviews as the inquiry into their daughter's disappearance centred on a group of three - two men and a woman. Local news reports said footage from a petrol station just outside Praia da Luz could now hold the key to the investigation.

It is believed a woman with a child matching Madeleine's description had been at the service station and attracted the suspicions of staff. Other reports, which have not been confirmed by police, said two men were also present.

Newspaper 24 Horas said the woman was in her 40s, blonde and appeared foreign. It said the image was passed to British police in an attempt to identify her and said the footage had been shown to those who gave witness statements to police to identify her. Correio Da Manha reported the CCTV footage included a car with a British number plate, and claimed the number had already been given to Interpol.

The newspaper said one theory was Madeleine had been kidnapped by one of the men with the complicity of a couple. Meanwhile, 24 Horas also reported a blonde woman seen near Madeleine's bedroom on the night of her abduction.

A Portuguese man in the town of Sagres, near Praia da Luz, had reported a foreign man trying to take a photograph of his daughter.

The man challenged the stranger who made off in a car which he then photographed with his mobile phone.

The incident is understood to have happened before Madeleine's disappearance and was reported to police on Monday.

Chief Inspector Sousa confirmed CCTV footage had been taken from several locations, but would not elaborate. In the UK, Crimestoppers said police were scrutinising four pieces of "very useful" fresh information. The tip-offs came among hundreds of calls from Portugal to a specially set up number. A spokeswoman for Crimestoppers said the numbers have been passed to Leicestershire Police, who are working alongside Portuguese police on the case.

The PJ's efforts are being boosted by information from the UK passed to them by Leicestershire Police, as well as the work of criminal behaviour experts from the Child Exploitation and Online Protection (Ceop) Centre. Among them is Superintendent Graham Hill, of Surrey Police, who is working with Ceop on secondment to the UK's "FBI-style" Serious Organised Crime Agency (Soca). He investigated the disappearance and murder of Surrey schoolgirl Amanda "Milly" Dowler.

An internet appeal asking for help in tracing Madeleine in English, Portuguese and Spanish has been issued by Ceop and the Virtual Global Taskforce (VGT) at the request of the Portuguese authorities.

It is carried jointly on ceop.gov.uk and virtualglobaltaskforce.com, which receives daily hits from 130 countries. Madeleine's maternal grandparents last night attended a moving service along with hundreds of others at their local church in England.

Susan and Brian Healy lit candles on the altar at Our Lady of Compassion RC Church in Formby, Merseyside. The family of the missing girl hugged each other and wept during the hour-long service held by Father Paul Seddon, who baptised Madeleine.

Friends and relatives of the McCanns in Glasgow have organised a vigil tonight at 7pm in St Andrew's Cathedral on Clyde Street. www.ceop.gov.uk www.virtualglobaltaskforce.com