The examination has been cancelled post the incident.
The crackdown followed just hours after the audio clips went viral in which two male voices can be heard leaking questions to a woman, ahead of the examination.
The voices are suspected to be of two law faculty members and the female voice is being allegedly attributed to the chairperson of a medical college, who is also enrolled as a student of LL. B third semester.
Later on Wednesday night, an FIR was registered at Hasanganj police station against three persons.
Lucknow University police outpost in charge, Abhay Kumar Singh, said, "Richa Mishra and Ashok Kumar have been named in the FIR and the third accused is still unidentified. We are yet to match the voice in the audio clips. We have launched a probe after registering a case under Uttar Pradesh Public Examinations (Prevention of Unfair Means) Act, 1998."
The incident has snowballed into a huge controversy for Lucknow University which is celebrating its centenary year.
Officiating Vice-Chancellor S K Shukla told reporters at a hurriedly convened press conference that several question papers of the third semester exam conducted in the first week of December had been leaked.
Shukla announced that two teachers were suspended because prima facie evidence (audio clip) points to their involvement.
"After hearing audio clips, it is clear that questions of several papers of LL.B semester III were leaked, compromising the sanctity of the exam process. Fresh dates of the exam will be announced later," he said.
A two-member committee comprising Prof (retired) SK Dwiwedi and former controller of examinations Prof (retired) Chaman Mehrotra has been formed to probe the paper leak.
Shukla said that he would request the state government to order a CB-CID probe.
He said that a fine of Rs 5 lakh has been imposed on the LU-affiliated private law college and it has been blacklisted as an examination centre. "We also sought CCTV footage and DVR tapes from the college, but nothing was found due to a glitch in cameras," said Shukla.
( With inputs from IANS )