Kweku Adeboli, a former trader convicted of fraud in 2012, is facing deportation to Ghana after being detained in the police station in Livingston.
He served four years of a seven-year sentence for a £1.4 bn fraud at Swiss bank UBS. It was released in 2015.
Foreigners sentenced to more than four years are automatically considered for deportation.
His spokesman said that was held in Scotland Dungaval immigration removal Centre.
The spokesman added that the ministry of the interior has indicated its intention to deport him on or shortly after September 10.
He was arrested when attending a monthly check-in at Livingston police station.
Adeboli is from Ghana, but has lived in the uk since the age of 12 years.