Thumb impressions of 4,250 students who were admitted to various medical courses this year in Tamil Nadu should be handed over to investigators, the Madras High Court said on Wednesday, as it asked if the CBI should probe the growing scandal involving proxies taking the National Eligibility cum Entrance Test or NEET. Adding the CBI as respondent in the case known as the NEET impersonation scam, the court said since the students gamed tests held even outside the state, the fraud could be an all-India phenomenon and many students in various states may have secured admissions through the manner.