They were waiting for an opportune time to strike at the Singapore International Jewelry Expo last Thursday.
But before the eight Chinese nationals could make their move, the police nabbed them.
Officers saw the men, aged between 31 and 49, behaving suspiciously in the Marina Bay Sands Expo and Convention Centre and went to check.
They found several plastic sachets of loose white-coloured stones on some of them and on the floor.
Later, the men were arrested for their intent to commit crime and the packets were seized for investigations.
They were repatriated on Tuesday after investigations were completed.
The sleight-of-hand approach - in which real gemstones are replaced with fakes - and distraction method are among the most common ways that thieves here use to commit thefts during jewellery fairs.
Other modus operandi include smash-and-grab, the use of children and hole-in-the-wall method where thieves dig their way through concrete or brick to enter the venues.
The suspects are usually well- dressed and operate in groups, the police said.
"Singapore is a safe and secure venue for us to hold international events," said Mr Edward Liu, 65, managing director of Conference and Exhibition Management Services, which organised the expo.
Eight cases of jewellery theft amounting to more than S$850,000 have been reported at three fairs in the last year. Six of them were solved while two are under investigations, police said.
Mr Liu said that Singapore's tight security at such events is one reason why it is one of the world's top destinations to hold international meetings and conventions.
About 200 exhibitors from 20 countries took part in the recent expo.
The show attracted about 10,000 visitors over four days and made more than S$40 million.
Police checked the venue before the show and advised organisers and retailers what to look out for.
During the show, they patrolled the venue and were "the first to be there and last few to leave", said Mr Liu.
This article was first published on July 12, 2014.
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