The Basel prosecutor said on Friday a 54-year-old Croatian is on the run and he has an international arrest warrant out for him for the Baselworld heist.
He was not named.
Authorities say eight people participated in the robbery, but they have not all been identified. No arrests have been made to date and a new appeal for witnesses was launched on Friday.
On March 30th, 2011, thieves made off with a set of four diamonds from a window, after distracting the booth staff.
The theft victim, an Israeli diamond dealer, realised his loss 15 minutes after the thieves had left the exhibition hall in the city of Basel untouched.
No diamonds have been recovered.
Investigations found the theft was carried out by an eastern European group active worldwide that specialises in stealing jewellery, diamonds and valuable antiques.
The fair, which held each March and is open to the public, has been targeted by thieves on several occasions. In 2009, a robber stole 13 million francs of jewellery, but was rapidly caught.
In 2007, thieves made away with more than a million francs worth of jewellery.
Despite the thefts, organisers have said they see no reason to change security measures.
Baselworld opens on March 8th this year. It brings together names such as Rolex, Dior, Hublot, Blancpain and Chopard, who present their most prestigious collections to some 100,000 visitors who come from around the world.