Sleuths questioning Umar Khalid and Anirban Bhattacharya, the JNU students held in a sedition case, are having a tough time cracking the duo with the former denying his involvement in any sloganeering and the latter challenging claims that the slogans were "anti-national".

Delhi Police today continued their interrogation of Khalid and Anirban but remained tight-lipped about developments in the case citing high court's order to maintain utmost secrecy.

The duo along with three other students, who gave a hard time to police as they searched for them across cities for over 10 days, resurfaced on the varsity's campus late on Tuesday night. Khalid and Anirban thereafter surrendered to police.

Police are also waiting for the production warrant of JNU Students' Union President Kanhaiya Kumar, who is in judicial custody, so that the three can be questioned together.

A police source said Umar and Anirban are presently being interrogated by two separate teams led by ACP rank officials.

The duo is being quizzed about the slogans raised during the February 9 event at JNU and the identities of others involved in the controversial event.

Police are also asking them what they had done as the "main organisers" to stop the raising of the alleged anti- India slogans during the protest against the hanging of Parliament attack convict Afzal Guru, the source said.

"While Khalid has maintained that he did not engage in any sloganeering, Anirban asked the investigators how the nature of slogans were anti-national at all," the source said.

While Khalid has told police he was in Ghaziabad after the event, Anirban's whereabouts during the period are still unclear, the source said, adding that police are also trying to track down the ones who sheltered Khalid and Anirban.

When Kanhaiya was questioned, he had dissociated himself from the controversial event, which led police to conclude that Khalid and Anirban -- whose names were earlier spotted on the posters for the programme -- were the main organisers of the event.

Khalid and Anirban have been shown the raw footage of the event and they have spotted some "foreign elements" that are yet to be identified.

While some of the outsiders are suspected to be from other central universities in the national capital, there also were people from other states, especially Jammu and Kashmir, at the protest, the source said.

Umar and Anirban were sent to three days' police remand by a city court yesterday after their surrender at midnight and subsequent arrest in the sedition case.

The South Campus Police Station, where the duo are being held, was turned into a makeshift courtroom following an order by Delhi High Court to "maintain confidentiality" during their remand proceedings.

During the hearing, the police demanded seven days' custody of the duo and also applied for the production warrant of Kanhaiya.

There was high drama yesterday as mediapersons were made to chase a police vehicle which was used as a decoy. Police resorted to such tactics following the "maintain confidentiality" order from high court.

The face of a person seated inside a vehicle leaving South Campus police station was covered with a muffler, prompting a posse of media personnel to chase it till another police station in south Delhi at around 2.30 PM.

With court proceedings held in a room there, South Campus Police Station was turned into a virtual fortress with at least two companies of police personnel deployed in the area and all roads leading to it blocked.

The magistrate arrived at 6.30 PM. Soon after, DCP (South) Prem Nath, who is heading the probe, was seen entering the police station. The hearing then continued for around two-and- a-half hours.

Earlier yesterday, Delhi High Court ordered police to "maintain confidentiality" during the remand proceedings of Kanhaiya, Umar and Anirban and directed the police to ensure that no one "suffers even a scratch" and there is no ruckus.

The court order came during the hearing on Kanhaiya's bail plea after it was informed that the JNUSU president along with Umar and Anirban were apprehending threat to their safety and security during production before Patiala House courts for remand proceedings.

Lawyers had allegedly assaulted Kumar when he was brought to Patiala House Court for remand proceedings in defiance of a Supreme Court order. Two days earlier, when Kumar was to be brought to the court, the same set of lawyers had thrashed journalists and JNU students and teachers.