London - Private detectives are investigating reports that a little girl calling herself "Maddy" was seen in the Netherlands just a few days after British toddler Madeleine McCann vanished during a holiday in Portugal in May 2007.

Reports in Britain said Wednesday that the possible sighting in Amsterdam of the missing girl was reported to Portuguese officers in June 2007.

But it was only made public with the release of previously secret police files earlier this week.

Madeleine's parents, Kate and Gerry McCann, have hired private detectives to search for Madeleine, who would now be 4.

The Dutch sighting was seen by detectives as the "most promising" of the lines of inquiry that are now being pursued.

According to the police documents, shop assistant Anna Stam, 41, said she spoke to a little girl aged 3 or 4 in Amsterdam who said her name was "Maddy" and replied to a question about her mother: "They took me from my holiday."

McCann family spokesman Clarence Mitchell said it was "tragic" that this kind of information should only be released now.

"It is harrowing to hear a child saying that. If it was Madeleine, it was a disgrace that it was not passed on."

According to reports Wednesday, the girl entered Stam's party shop in early May 2007 with a man and a woman and two other children, according to a witness statement to Dutch police.

The man - who "did not look like a nice person" - appeared to be speaking Portuguese but the woman spoke English and told Stam they had a small circus in France.

Stam was at the back of the shop when the young girl approached her and asked in unaccented English, "Do you know where my mummy is?"

On being told that her mother was a little further back in the store, the child replied, "She is not my mummy," and added, "She is a stranger, she took me from my mummy."

Stam said she thought the girl looked "very much like" Madeleine apart from the colour of her hair.

The report was sent to the Portuguese authorities on June 18, 2007, but it was not clear what action was taken, British media said. (dpa)