The revelation was made Friday in U.S. District Court in Central Islip by Judge Joanna Seybert.
According to an affidavit filed by FBI agent Angela Jett, Brooks concealed from the court several million dollars he had overseas, including $3.6 million in British pounds, U.S. dollars and euros in a safe-deposit box in London; more than $1 million in a bank account in the Republic of San Marino, an independent state in Italy, and an unknown amount of money in a safe-deposit box in Switzerland.
The failure to report these assets was a violation of Brooks' bail conditions, according to Seybert.
Brooks, who was the head of one of the largest manufacturers of body armor for the U.S. military, had been released on bail to his Manhattan apartment since January 2008 after being charged with looting his company to support an over-the-top lifestyle.
Among other things, federal prosecutors said Brooks used company assets to pay for a multimillion bat mitzvah for a daughter and for a $101,000 jewel-encrusted belt buckle in the shape of the American flag.
Federal officials declined to comment on the arrest.
Jury selection in Brooks' trial is scheduled to start next week in Central Islip.
A hearing on the bail revocation is expected to continue this afternoon.