The Belgian capital's emblematic Manneken Pis statue of a little boy taking a very public leak, beloved by millions of tourists, is getting a thorough examination to prove whether he is the real deal.

The small statue standing about 60 centimetres (23 inches) tall in a fountain in the heart of Brussels has suffered many indignities since he was first put up in the early 1600s, prompting the authorities to replace it with a replica in the 1960s.

The original is supposedly in the nearby Brussels Museum where it was lovingly restored in 2003 but researchers now think the little cherubic bronze they have there may not be the genuine article after all.

"Looking at the Manneken Pis closely, I realised that its history is very murky and that actually we do not know whether it is the original or not," Geraldine Patigny, a research student at the Free University of Brussels (ULB), told AFP.

In 1619, the Brussels authorities asked sculptor Jerome Du Quesnoy the Elder to make the statue of the small boy urinating -- according to one of many legends, to put out a fire caused by besieging troops and so save the city from destruction.

The statue was stolen several times over the years, most notably in a well-documented case in 1817 when supposedly it was put back in its place of honour. It was stolen again in 1965.

Patigny believes the statue that was returned to the fountain in the 19th century may have been in fact a replica.

"After that (theft), we have no more trace of the original which apparently is only found again in 1966, in two pieces, in a Brussels canal," Patigny said.

The statue, believed to be the original, was then handed to the museum for safe keeping.

"The historical record is very confused and there are holes in it. There are accounts in local publications or in folklore but there is nothing really concrete in the archives," Patigny said.

Researchers are hoping that X-ray images and other tests will provide the answer, specifically on the chemical composition of the bronze.

"We are looking especially to see if it includes nickel," said Amandine Crabbe, a researcher at the Flemish Free University of Brussels (VUB).

"If it is present, that would mean it most likely dates from the 19th century," Crabbe said.

"If it is absent, then that makes it more likely that it is the original, although it is never possible to be 100 percent certain."