The policeman leading the hunt for missing youngster Madeleine McCann said Portuguese police are doing all they can to find her but added that he could not be sure she is still alive.

Little information about the police investigation has been made public, prompting criticism that police are not doing enough to find the missing three-year-old.

But Chief Inspector Oligeario Sousa said yesterday: "I want to assure the family and all the people involved that the professionals are doing the best they can."

On Saturday, Portugal judicial police said they believed that Madeleine was still alive but, yesterday, the Chief Inspector admitted: "We have no facts to sustain that the child is alive or not.

"We are searching for the child until the moment she appears.

"We can say nothing more because we are not magicians.

"All the authorities involved are doing the best efforts to recover the child."

The blow came just hours after Madeleine's mother, Kate, made a powerful direct appeal to anyone holding her daughter to let her go.

With her husband Gerry beside her, she said: "We would like to say a few words to the person who is with our Madeleine, or has been with Madeleine.

"Madeleine is a beautiful, bright, funny and caring little girl. She is so special. Please, please, do not hurt her.

"Please do not scare her, please let us know where to find Madeleine or put her in place of safety and tell somebody where. We beg you to let Madeleine come home."

She added: "Please give our little girl back", and then repeated this final phrase in Portuguese, saying: "Por favor, devolva a nossa menina".

The toddler disappeared on Thursday night while she was left with her brother and sister, two-year-old twins Sean and Amelie, in a holiday apartment. Her parents had been dining in a nearby restaurant and checking on them regularly.

The young girl was wearing white pyjama bottoms with a small floral design and a short-sleeved pink top with a picture of Eeyore on it when she vanished.

Yesterday's chaotic press conference began more than two hours late and even when it started, Chief Inspector Sousa said that he could reveal little about the case because of the restrictions of Portuguese law.

He insisted that, as a father himself, police were doing everything they could to find Madeleine.

Asked whether he was keeping the family fully informed, he said: "The family is the number one interest in the case but even then, they must be a little far from the investigation."

Speaking of the McCanns' pain, he said: "What they are feeling now I can't imagine, I am a father too, all the police, we are fathers and mothers.

"It is probably pain with no measure they are feeling."

Answering questions which were fired in English and Portuguese, Chief Inspector Sousa repeatedly said that he could not publish an artist's impression of a man seen acting suspiciously because he feared it could harm the case.

The hunt was extended yesterday by up to nine miles around Praia da Luz, as police said they have found evidence she was abducted but refused to disclose details.

Officers also revealed that Interpol has become involved.

There has been speculation in the Portuguese media that police suspect a Briton or Britons may be behind the abduction.

Broadcaster RTP interviewed Barra da Costa, a former inspector in the Judicial Police, PJ, who said the force believed her abductor may be from the UK.

He said investigators told him that a working description of the suspect being used by detectives suggested someone of English appearance.

The former police officer said the apparently meticulous planning, without leaving forensic evidence, could also point to a British rather than Portuguese intruder.

Experts have put together an artist's impression of a "suspect" but have not publicly revealed details and it is believed it only shows the back of a man's head and his hair.

It was also reported yesterday that police are investigating a claim a man was seen dragging a young girl along towards a marina in the nearby town of Lagos.

Around the marina at Lagos, which was busy with British tourists yesterday, bars and restaurants were displaying photographs of Madeleine to jog customers' memories.

Police have taken records of all boats booked into the marina right through from April 27 to May 6.

Marques Pereira, harbour captain at Lagos, admitted that they were searching for a body as well as other evidence.

He told Portuguese newspaper Diario de Noticias: "We can't afford to discard or abandon evidence such as clothes, shoes or even a body."

Joao Riveiro, who works on the marina staff, said large numbers of police officers have been searching the area.

A small party of around 20 volunteers was searching forests and rough ground around the outskirts of the village of Espiche.

Along the nearby coast police have checked a cave complex at Ponta da Piedade, with the help of volunteer canoeists.

Villagers in Madeleine's home village will today hold a silent vigil to show they are thinking of the McCann family.

Resident Valerie Armstrong, who is one of the organisers, told GMTV that people would be encouraged to light a candle or to tie a red ribbon around railings at the War Memorial on the village green at Rothley, Leicestershire.

Madeleine's great uncle Brian Kennedy said it was a "wonderful idea".

Mr Kennedy told GMTV that Madeleine's mother must be under tremendous strain but seemed to be keeping her spirits up.

He added: "But as the days go on it must be very difficult."

Mr Kennedy, a retired headmaster who lives a few streets away from the McCanns, said any analysis of the police investigation should take second place to the hunt to find Madeleine.

He said: "I think the main thing is to keep up the search. Any shortcomings should be looked at afterwards."

Staff at Leicester's three hospitals will join in prayer today for the McCann family.

Madeleine's father is a consultant cardiologist at the city's Glenfield Hospital.

Colleague Doug Skehan, also a consultant cardiologist, said: "Gerry is a popular, hard-working colleague, for whom we have great affection. We are greatly concerned by the disappearance of his daughter.

"Staff from our three hospitals will join together to pray that she is returned safely to her family."

The hospitals' chaplaincy team were due to lead prayers at Glenfield Hospital, in Groby Road, from 1pm.

Copyright Press Association 2007