Netflix documentary 'The Disappearance of Madeleine McCann' has claimed that the three-year-old could have fallen down a storm drain after sh was reported missing from her Portugal apartment in 2007.

Before police mined sinister alternatives such as abduction and murder, those involved early on in the case considered the theory to be a highly likely possibility.

Authorities left no stone unturned back in 2014, opening manholes and combing stormwater drains in the region's underground sewage system to look for remains of the toddler, The Sun reports.

On May 3, 2007, Maddie was on holiday with her parents and family friends at a resort in Praia da Luz, when she unexpectedly disappeared from her bed. Gerry and Kate McCann, her parents, were having dinner at the hotel's restaurant at the time and had left her sleeping with her siblings. They realized that she was missing at about 10 pm.

The infamous missing child case is the focus of the new eight-part documentary by Netflix, and has reignited interest in the case that has baffled investigators and fueled conspiracy theorists.

Appearing in the documentary, local property developer Barry Sadler said, "When you leave the main road and the tourist areas, there are wells all over the place. I'm sure the child didn't wander up there them-self, but you don't know, accidents could happen."

Meanwhile, journalist Jon Clarke revisited initial claims that Maddie may have fallen into a construction workers' trench located nearby the resort where they were staying.

 

"There was a big trench... leading all the way down the road about this wide and 6ft deep and there were two or three guys working in the trench," he said. "You kind of think, could she be down there, could she have fallen down there? Could they have buried her by accident?"

That said, without the discovery of the body, that theory was ruled out.

Instead, investigators first resorted to accusing her parents of being involved before eventually focusing on unknown kidnappers.

"Perhaps the most telling sighting of all is that of Carole Tranmer who had been out to see her aunt who was living in the apartment immediately above the McCanns. Carole was looking out of the window," investigator and author Anthony Summers explained in the Netflix documentary.

"She said: 'Looking down below the McCann flat I saw someone come out of the ground floor apartment closing the gate very carefully and quietly. It looked very strange to me. He looked to one side and the other, shut the gate and walked very quickly below. This is on the afternoon of the day Madeleine is going to disappear.' What had struck her as peculiar, she said, was 'the way the man had closed the little gate down there. It was his furtiveness that got my attention. The man had moved stealthily as if he didn't want anyone to know he was coming or going'."

"That has to be significant in any investigation of this case," he added.

The documentary also expresses fears that the toddler could have been trafficked. Patricia de Sousa Cipriano, the president of the Portuguese Association of Missing Children, said in the documentary: "We have information that our country is used by traffickers to pass children to other countries. They enter the country through the Algarve and then they go to Spain, to France, to Germany, to be exploited. They have a very strong structure that allows them to move human beings from one country to another in a matter of hours. It's frightening because it's very easy."

The Netflix documentary has been fiercely criticized by Maddie's devastated parents, who said it "won't help" the search. According to them, the controversial new movie could "fuel conspiracy theorists" and do more harm than good.

Kate wrote her own account of what happened that evening in a 2011 book titled 'Madeleine: Our daughter's disappearance and the continuing search for her', revealing little Maddie's haunting words to her the day before she disappeared. "Why didn't you come when Sean and I cried last night?" Maddie allegedly asked her.

"Madeleine didn’t answer or elaborate," Kate continued. "Gerry and I were disconcerted. Could Madeleine and Sean have woken up while we were at dinner? If so, it was worrying, obviously, but it didn’t seem very probable."