Notice has been issued to 30 Jawaharlal Nehru University (JNU) students, including Kanhaiya Kumar, to join the probe into alleged raising of anti-national slogans on the campus in February last year, Delhi Police said.

"They have been given time by the Delhi Police Special Cell to be present at the administrative block of JNU from 12 p.m. onwards between April 28 and April 30," a senior police officer said.

A copy of the notice has also been sent to the JNU Vice Chancellor.

"Their statements will be recorded as the Investigating Officer has been directed to start the probe afresh," the officer told IANS, adding that "Legal action will be taken if the students failed to join the probe".

A fresh probe was ordered by the top brass of Delhi Police, which went through the draft charge sheet prepared by the Special Cell.

The Legal Wing, which also got to study the draft, found that more probe was required to prove their offence, the officer said.

"The Investigating Officer has been told to complete the recording of the students' statements within three days," he added.

A final report along with the draft charge sheet was submitted to Delhi Police Commissioner Alok Kumar Verma in January. The officers connected with the probe had then said that he would give the go-ahead to file the charge sheet.

"Since it is a case of sedition, prior approval of the Lt. Governor's office is also required," he said.

"The draft report said there is enough evidence to prosecute Umar Khalid and Anirban Bhattacharya for sedition. It identified nine 'outsiders' who raised anti-India slogans," the officer said.

The case was transferred to the Special Cell in March 2016.

The Patiala House Court in August 2016 granted regular bail to JNU Students Union President Kanhaiya Kumar and two others — Khalid and Anirban — in the sedition case.

The Delhi High Court in September 2016 extended the interim relief given to Khalid and Anirban, who have also been charged with sedition.

Khalid, Anirban and Kanhaiya are accused by Delhi Police of raising anti-India slogans on the campus at a meeting organised on February 9 last year in memory of 2001 Indian Parliament attack convict Afzal Guru.