The Chinese thief who reportedly swallowed a $14,000-worth diamond at the biggest jewellery exhibition in Sri Lanka actually consumed a fake stone, according to police.

Chou Wan, 32, was arrested by Sri Lanka authorities after ingesting what was believed to be a 1.5 carat diamond at the Facets opening day exhibition in Colombo.

Having given Chou some laxatives to recover the stone, police were astonished to find out that what he passed was in fact a fake copy of no financial value, as certified by the National Gem and Jewelry Authority.

Police now believe that Chou had an accomplice who cautiously swallowed the real diamond before Chou theatrically ate the imitation copy, to divert the attention of the gem's owner Suresh de Silva.

Authorities are now looking for another Chinese man who was seen behaving suspiciously with Chou at the exhibition.

"We suspect that, as habitual offenders, this group were in the habit of swapping real stones for fake ones," police spokesman Ajith Rohana told the BBC.

However, according to de Silva, the real thief did not actually eat the diamond but just run away with it.

The man believes the two thieves were trying to swap his gem with a fake one, when he spotted the suspect activity and apprehended one of them: Chou. The other men fled.

Chou then ate the fake diamond in a panic when police arrived, de Silva said, adding that the man had another six fake gems in his pockets.

Sri Lanka is well known for its highly treasured gems, although it does not mine diamonds. It is most famous for its blue sapphires, and visitors are known to come from around the world for jewellery exhibitions in the country.