Akshat Awasthi and Rohit Shah, ABVP members, whose faces emerged during a TV channel sting, refused to join the investigation, police said, hoping they would join the probe on Tuesday.
The official said the police called up a "masked woman", identified as Komal Sharma, but her phone was found to be switched off. "A notice has been sent to her to join the investigation. She is a student of Delhi University's Daulat Ram College," said the official.
The police have so far issued notices to 9 accused asking them to join the investigation into the JNU violence. Seven out of the 9 suspects are from Left organisations. Out of the seven accused, three JNUSU President Aishe Gosh, Bhaskar Vijay and Pankaj joined the investigation on Monday.
Aishe Gosh was questioned separately today, a senior police officer said, adding one of the questions the police asked her was who had hit her and whether she could identify the suspect.
She was also asked how many stitches she received for her head injury.
Ghosh had told a channel that she was hit by an iron rod and that she received 10 stitches on the upper part of her forehead.
The other suspects, Bhaskar Vijay and Pankaj, were questioned together by a Special Investigation Team.
The police are trying to coalsce all the information to form a sequence of violence that rocked the university on Jan 5.
The police have decided to send a legal notice to 37 more people, part of WhatsApp group involved in the violence.
( With inputs from IANS )