The special investigation team (SIT) probing the topper scam on Wednesday procured a non-bailable arrest warrant against Aastha Srivastava, one of the five state toppers in the Intermediate science stream exam last year.

Police investigations have revealed last year's exams were rigged as well; Aastha was a student of Vishun Roy College in Vaishali, epicentre of the scam.

"Apart from this student, the police have got non-bailable warrants for four more people," Patna SSP Manu Maharaaj, head of the SIT, told The Telegraph. "They have been identified as Vishun Dev Rai, father of (Vishun Roy College owner and suspected scam kingpin) Bachcha Rai, Bachcha's wife Sangeeta Rai, his father-in-law Ram Nagina Rai and Rajvanshi Rai, a close relative of Bachcha. All of them have been found to have been involved in the scandal."

Last year Vishun Roy College student Vishal Kumar was declared science stream topper, replacing Vikas Kumar, student of a different college who had been declared the topper first. Vikas had protested and approached many Bihar State Examination Board officials including then board chairman Lalkeshwar Prasad Singh. A state government-appointee committee had recommended action against Bachcha and his college but Lalkeshwar had chosen to ignore the report.

"The police had recovered two biology answer copies of Aastha," Maharaaj said. "One is the original paper issued by the board while other is an identical answer sheet - which used to be printed by Bachcha - without the board's watermark. Both answer sheets have the same handwriting but the one provided by Bachcha has been written very neatly and has all answers absolutely right. If the examination centre couldn't be rigged by Bachcha, he used to set the evaluation centre of his college and the original answer sheets were replaced by the fake ones. The board, under Lalkeshwar, never used to object."

Invigilators at the GA Inter School in Vaishali, the examination centre for Vishun Roy College students, will also be facing action, the officer said.

"The school's principal Shail Kumari is already behind bars," he said. "The centre head of the institution was changed for two days while the examinations were on. It is being investigated. There were a lot of irregularities going on in the examination centre including two candidates having the same details and registration number appearing in the examinations. The police are sure that the invigilators played a major part in the scandal."

The special vigilance court on Wednesday deferred the bail petition of this year's disgraced Intermediate arts topper Ruby Rai until July 30.