A source close to the investigation told the Associated Press that the individuals will be formally charged in the coming months.
However, they did not reveal whether Mr Madoff's wife, sons or other family members would be the targets of any indictments.
Mr Madoff was sentenced to the maximum 150 years in prison on Monday (June 29th) after he had pleaded guilty to 11 felony charges including securities fraud, money laundering and perjury.
The 71-year-old financier had always insisted he had orchestrated the decades-long fraud alone without the knowledge of business associates or family members.
Following Mr Madoff's sentencing, his wife Ruth said in a statement that she felt "betrayed and confused" by his actions, NY1 reports.
"The man who committed this horrible fraud is not the man whom I have known for all these years," the statement read.