HOUSTON, Texas (KTRK) -- Federal prosecutors in Houston say nearly 100 people have been charged in a massive marriage fraud scheme, and a family in Southwest Houston is at the heart of the indictment.A federal grand jury has indicted 96 people in the alleged scheme with operations in Houston and Vietnam.The charges allege that the mastermind behind the scam is Ashley Yen Nguyen AKA Duyen, 53, of Houston.Prosecutors say Nguyen operated the Houston-based organization out of her home on High Star Drive and had associates operating throughout Texas and Vietnam.Prosecutors say the scam involved the creation of sham marriages in order to illegally obtain immigration status."These arrests mark the culmination of a comprehensive year-long multi-agency investigation into one of the largest alleged marriage fraud conspiracies ever documented in the Houston area," said Special Agent in Charge Mark Dawson of Immigration and Customs Enforcement's Homeland Security Investigations. "By working together with our partners from various federal law enforcement agencies we have sent a resounding message that we are united in our effort to disrupt and dismantle criminal organizations that seek to circumvent U.S. law by fraudulent means."In court Monday, Nguyen, her daughter, and her common-law husband were among a dozen defendants who made their first appearance.Nguyen's daughter was granted bond, but Nguyen and her common-law husband were ordered held pending trial."The government in these detention hearings always try to make these salacious kind of statements and arguments," said Nguyen's defense attorney Mar Carter. "They were also making a point to let the judge know she is a naturalized citizen that is somehow less than someone born here."