The declaration of results for Matriculation, which was scheduled for tomorrow, has now been deferred to June 26, the BSEB said in a statement released here.
The principal of the school - situated at Gopalganj district - was summoned here by the BSEB and later detained by police for interrogation.
The latest episode has further tarnished BSEB image which had drawn widespread condemnation in the wake of "toppers scam" when non-deserving students were declared top rankers in Arts as well science streams out of materialistic considerations in 2016.
"Pramod Kumar Srivastava, the principal of SS Girls's Senior Secondary High School had registered an FIR on Sunday stating that over 200 bags, containing more than 40,000 answer scripts evaluated at the premises and kept thereafter in the strong room, were missing", SHO of Town police station in Gopalganj, Ravi Kumar, told PTI-Bhasha over phone.
The SHO said that in the FIR, Srivastava had named some non-teaching staff who had been entrusted with manning the school building.
BSEB Chairman Anand Kishor said "Srivastava was called to the Board headquarters here for questioning. He was later detained by the police for further questioning".
Deputy SP, Law and Order, Patna, Manoj Kumar Sudhanshu confirmed the detention of Srivastava.
However, both Kishor and Sudhanshu declined to divulge details of the investigation.
The BSEB later issued a press note stating "the DM and the SP of Gopalganj have been directed to ensure recovery of the barcoded, evaluated answer scripts, identify the culprits and take action against them as per law".
The Board also announced that the results would now be declared on June 26 but claimed that disappearance of the answer scripts will have "no effect on the overall results nor on preparation of the list of top-ranking students".
"All the evaluation centres have provided the BSEB headquarters with award sheets stating the marks awarded to each candidate. Hence, we are already in possession of the respective scores of even those candidates whose answer scripts have gone missing", the BSEB release said.