(CNN) The family of a Chinese student who was admitted to Stanford University paid $6.5 million to the central figure in the US college admissions scandal, a source with knowledge of the investigation says.

It has not been determined whether the student's parents were seeking an advantage to get their daughter into Stanford with the payment to Rick Singer, the source said. There's still the possibility they may have done nothing wrong but that will be determined by investigators, the source added.

Morgan Stanley adviser Michael Wu referred the parents to Singer, the source said. A spokeswoman for Morgan Stanley told CNN that the company is cooperating with investigators.

Wu "was terminated for not cooperating with an internal investigation into the college admissions matter," the spokeswoman said.

The student, her parents and Wu have not been charged in the scandal.