The police special investigation team (SIT) on Friday recovered jailed Intermediate arts topper Ruby Rai's "missing" answer sheet amid other copies in a locked room at the Rajendra Nagar-based Government Boys Senior Secondary School.

The home science answer sheet had gone missing when the police began probing the education scam a month back. The police said the sudden find raises questions - why didn't the police found it when the Bihar School Examination Board (BSEB) was handing over to SIT answer sheets of the four accused toppers whose results have been cancelled?

"The police had written to BSEB about the missing answer sheet. Today (Friday), BSEB suddenly told SIT her copy had been found," Patna SP (central) Chandan Khuswaha told The Telegraph.

"The answer sheet, in which she scored 57 marks in theory and 29 in practical, was recovered from a room at the Rajendra Nagar School, evaluation centre for Vishun Roy College. It has been said earlier that Lalkeshwar Prasad Singh (former BSEB chairman and scam mastermind) had brought copies of the said toppers to his office before the intermediate results were to be announced. The police need to know why the copy couldn't be found earlier and why it surfaced suddenly today."

The answer sheet bears the same marks as in Ruby's cancelled result. During an interview to a television channel, Ruby had said that "prodigal (her spelling of political) science" deals with cooking.

Police investigations show Lalkeshwar's wife Usha Sinha had talked to Bachcha Rai (Vishun Roy College principal who paid Rs 15 lakh to Usha for declaring Shalini Rai, his daughter, and Ruby Rai, a distant relative, toppers) more than 100 times on the phone between February (when intermediate exams were held) and May (when results were declared).

Also, cell phone tower details indicate Bachcha and Lalkeshwar had talked over 60 times during the same period.

Also on Friday, Patna High Court advocate Manibhushan Pratap Sengar filed a PIL demanding a CBI probe into the scam. Sengar said in his PIL that since senior government officials and a few politicians were involved in the scam, only a fair, clean, transparent and unbiased inquiry would help unearth the truth.

The petitioner expressed feared that in absence of an enquiry by an independent agency, the investigation conducted by the state government would be a farce.

The petitioner has also asked the court to pass an order putting an end to giving further affiliation to such types of colleges and to cancel the affiliation of those colleges indulging in such activities.