Police officers set a line near the Casa Liliana which Robert Murat shares with his elderly mother	Robert Murat believes the search will prove his innocence

Police investigating the abduction of Madeleine McCann yesterday spent a second day digging up the garden of Robert Murat, the only official suspect, at his home yards from where she was abducted.

The search continued while Kate McCann, Madeleine's mother, spoke of her regret at leaving her three children alone at the resort while she and her husband ate at a nearby restaurant.

Intense police activity in the past 48 hours has sparked hope of a breakthrough, more than three months after Madeleine went missing.

It is claimed that two sniffer dogs from Britain and their police handlers have found new clues at the apartment in Praia da Luz where she disappeared.

Last night the focus of the inquiry remained on Casa Liliana, which Mr Murat shares with his elderly mother. The home is 150 yards from where Madeleine was snatched on May 3.

As many as 10 officers spent Saturday clearing thick vegetation. Sniffer dogs inspected the premises.

It is thought detectives used scanners that can detect anything buried deep beneath the ground.

Mr Murat, 33, has been the only official "arguido", or suspect, since May 10, when he was detained by police. He was questioned for a second time last month but detectives have never found any evidence to arrest him formally.

He was on the premises yesterday and has told friends he welcomes the search, which he believes will reveal nothing except his innocence.

Police remained silent over why they had searched Mr Murat's home a second time.

"We have reached a phase in the investigation where we are trying to evaluate everything," one Portuguese police source said.

"We are going through all the interviews, facts and clues - with the help of British profilers - to ensure nothing has been missed or left out. At the moment there is still only one arguido."

Police are yet to resolve alleged inconsistencies in statements given.

Friends of the McCanns said they saw a man near the family's apartment helping with the search on the night Madeleine vanished.

Mr Murat maintains that he was at home with his mother all evening when the girl was snatched from her bed.

In the first interview she has given without husband Gerry, Mrs McCann, 39, said: "We are just so desperately sorry.

"Every hour now, I still question, 'why did I think that was safe?' If I'd had to think for one second, 'should we have dinner and leave them?', I wouldn't have done it.

"It didn't happen like that. I didn't have to think for a second, that's how safe I felt."

She said she tucked Madeleine into bed that night, and her daughter last words to her were: "Mummy, I've had the best day ever. I'm having lots and lots of fun."

Mrs McCann also described her joy at the birth of Madeleine, her oldest child, after five years of trying for a baby.

She said: "I wanted to be a mother. Then, when we were trying for a baby and it wasn't happening, it was really hard.

"The longer it went on, the harder it was. I saw my friends having children and I was really delighted for them, but it made me feel sad, too. We tried unsuccessfully for several years to conceive.

"There came a point when we admitted we needed help. I was so desperate to have a child I'd try anything. I know IVF isn't everyone's choice but I wanted to try it.

"We had one unsuccessful attempt before Madeleine and that was very hard. When I got pregnant with Madeleine it was just fantastic."

Asked what message she would send to her daughter, Mrs McCann said: "I would tell her that we love her. She knows we love her very much. She knows we are looking for her, that we are doing absolutely everything and we will never give up."

Mrs McCann, a GP, and her husband, a consultant cardiologist, from Rothley, Leics, are both on compassionate leave.

Meanwhile, Belgian police are investigating an alleged sighting at a café in Tongeren.

They are awaiting results from DNA tests on a milkshake bottle and straw used by a girl matching Madeleine's description.

One witness, a child therapist, said the couple were acting strangely and the child seemed nervous. "It was obvious that the couple were not her parents," she said.

The woman telephoned police but the trio left before officers arrived.