The Guwahati Police on Wednesday arrested a Joint Entrance Exam (Mains) candidate in Assam and his father for allegedly using a proxy to write the exam, The Times of India reported. Three employees – identified as Hirulal Pathak, Pranjal Kalita and Hemendra Sharma – of the agency that conducted the test were also arrested.

All the accused were charged with cheating by impersonation, criminal conspiracy and criminal breach of trust.

Neel Nakshatra Das had scored 99.8 percentile in the exam for admissions to the Indian Institutes of Technology and other top engineering colleges in the country, according to Hindustan Times. His father, Jyotirmoy Das, is a doctor at a prominent hospital in Guwahati.

The arrests were made based on a complaint filed by a man named Mitradev Sharma. The complainant alleged that the candidate marked his presence at the exam hall biometrically and then came out with help of an invigilator. He added that another person wrote the test for him.

Sharma also alleged that the candidate’s parents paid around Rs 20 lakh to a private coaching institute to help him commit the crime.

“The matter came to light after the candidate reportedly admitted this during a phone call, which was recorded,” Additional Deputy Commissioner (West) Suprotiv Lal Baruah told the Hindustan Times. “As of now, we haven’t come across any other case of misrepresentation during the test.”

Guwahati Police Commissioner MP Gupta, however, told NDTV that the case may be part of a bigger scam. “The staff of the testing centre in Guwahati is also involved,” he said. “We are searching for more people [suspects in the case]. This might not be a one-off case but may be part of a larger scam.”

The police alerted the National Testing Agency about the incident and sealed the examination centre.

Corrections and clarifications: An earlier version of this article reported that the candidate was a topper. The error has been corrected.