This article appeared in the Guardian  on Wednesday February 19 2003 . It was last updated at 01:29 on February 19 2003.

Armed with inside knowledge and a taste for the spectacular, a gang of thieves has managed to pull off the biggest gem theft that Antwerp - the diamond-cutting capital of the world - has ever suffered, officials admitted yesterday. The operation sounded like a film script, but police said it was conducted with no melodrama, no shoot-out, no screeching tyres and no blood. A gang had simply walked into one of the most heavily guarded buildings in Antwerp's diamond district and walked out again - without meeting a soul.

Although the authorities insist it will take days to provide an accurate estimate of the value of the stolen stones, the figure is said to run to tens of millions of pounds. Antwerp's close-knit diamond community can scarcely believe what has happened.

As the world's largest distribution centre for diamonds, the Belgian city has gone to extraordinary lengths to keep its lifeblood safely under lock and key but the audacious and suspiciously well-informed thieves still managed to slip in and out unnoticed and take exactly what they wanted.

"It is impossible and yet it happened," a stunned diamond merchant, Marcel Fuehrer, told the daily Het Nieuwsblad yesterday. Although the theft is thought to have taken place on Sunday night, it was only on Monday morning that anyone noticed that anything was wrong. Dazed diamond dealers arrived at work to find 123 of the city diamond centre's supposedly Fort Knox-like 160 safes empty. The safes' reinforced metal doors were ajar and documents and even gems were scattered on the floor in the cavernous cellar vault. The thieves had been in a hurry to make their exit.

Documents certifying the stones' authenticity, their origin and the fact that they had not been imported from conflict zones were also lifted.

The vault's main door - which is 20cm thick and bomb-proof - had not been tampered with, and the thieves had had the courtesy to close it behind them. "There were no signs of forced entry," an industry source told the Guardian yesterday. "There are cameras, sophisticated alarms, 24-hour security guards on every main entrance and every exit, and even cameras in the vault - so how these people got in undetected is a mystery.
"They must have had the necessary security passes and known exactly where the cameras were. Everyone suspects it was an inside job."

Most of the safes were leased by diamond dealers and polishers who work in the offices above the vault which is situated in the unprepossessing, modernist Grimbergen building at 9-11 Schupstraat. Only a fraction of them were rented by "outsiders".

Early estimates suggest that the emptied safes belong to 70 individuals or organisations. The police confirmed last night that they were questioning all of the safe owners as well as anyone who works in the diamond centre. Not just anyone can hire a safe - people who want a secure deposit box have to undergo a rigorous process of security screening.

The precise value of the gems, like the manner of the break-in itself, remains a mystery. In the murky and often secretive world of diamond dealing nobody wants to guess how much the gems are worth although the "damage" is said to be far greater than a previous heist in 1994. Only five safes were emptied on that occasion and stones worth about £3m taken. If the 123 safes in the latest theft were stuffed with a similar quantity of gems, that would put their value somewhere in the region of £74m, although experts are cautious. "We shouldn't extrapolate but it is sure that the total will be much larger now," said Youri Steverlynck, a spokesman for the city's High Diamond Council, the body which oversees the diamond trade. "We are certainly talking about many millions." Other, more pessimistic, industry sources speak of "tens of millions".

"This is the biggest robbery of diamonds Antwerp has ever seen," said one, noting that all the Flemish daily newspapers claimed it was the most audacious and damaging in the city's history.

The authorities said they were working as quickly as possible to quantify the losses. "We are in the midst of making a full inventory [but] it is far too early to say something about the total loss," said Leen Nuyts, a spokeswoman for Antwerp's prosecutor, yesterday. The diamond industry is shell-shocked and embarrassed by the robbery. "We will have to see to what extent the security system failed," said Mr Steverlynck yesterday. "[This] will hurt Antwerp's image as a diamond centre." Nor can the authorities believe that the gang managed to make off with so many diamonds. "[They must have been in the vault] for hours, or there must have been a great many of them," said Ms Nuyts.