The Bihar government had sought Singh's resignation yesterday, but he refused to do so initially.

A show cause notice was then issued against Singh this morning, forcing him to quit his post.

Meanwhile, India Today has discovered that while answer sheets from all other schools in Vaishali district were sent to Kaimur and Ara for evaluation, only the ones from Bishun Rai College were sent to Patna's Boys' High School.

The Arts and Science toppers in the Plus Two exam - Ruby Rai and Saurav Shrestha respectively - had taken their examination at Bishun Rai College.

The Special Investigation Team probing the topper scam yesterday raided the school where the answersheets of the candidates from Bishun Rai College are kept.

The prinicipal of the school, according to sources, has claimed that seal of the envelope in which answersheets of Bishun Rai College was sent to him was already broken.

Five people, including the principal of the GA Inter College, which was the examination center for Bishun Rai College students, have been detained and being interrogated.

The centre superintendent of Patna Boys' High school Viseshwar Yadav has also deen detained by the SIT.

An FIR has been filed against Science toppers Saurabh Sreshtha, third topper Rahul Kumar and Arts topper Ruby Rai - all students of Bishun Rai College.