Caucher Birkar, 40, was one of the four joint winners of the medal -- regarded as the Nobel Prize of mathematics -- who were given the award at the International Congress of Mathematics on Wednesday, the Guardian reported.
Birkar had left the medal in a briefcase with his cellphone and wallet on top of a table in the pavilion where the event was being held. The security team later found the briefcase under a bench but the medal was missing.
Brazilian newspaper "O Globo" has claimed that the thief had already been identified from a security camera footage.
Organisers lamented the theft in a statement: "The organising committee of the International Congress of Mathematics profoundly regrets the disappearance of mathematician Cauchar Birkar's briefcase, which contained the Fields medal he received at this morning's ceremony."
"Images recorded at the event are being analysed. The organising committee is cooperating with local police authorities in their investigation," they said.
The ceremony was held at Riocentro, a convention centre on the western edges of Rio - a city struggling with soaring crime rates.
Birkar was born in Iran and moved to the UK as a refugee two decades ago.
The other three winners of the medal were Indian-origin Stanford University professor Akshay Venkatesh; Alessio Figalli of the Swiss Federal Institute of Technology, and Peter Scholze of the University of Bonn.
The Fields Medal was first awarded in 1936 and since 1950 is presented every four years to up to four mathematicians under 40.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
