Investigators have recovered pieces of partially burnt mobile phones that had been destroyed by Lalit Jha, alleged "mastermind" of the Parliament security breach, Delhi police sources said on Sunday.

"Fragments of some broken and burnt mobile phones have been recovered from Nagaur in Rajasthan. We have added IPC (Indian Penal Code) sections related to the destruction of evidence against the accused," a Delhi police officer said.

Jha is alleged to have fled to a friend's place in Nagaur after Wednesday’s stunt, when two youths intruded into the Lok Sabha and released smoke from canisters while two others did so just outside Parliament premises while chanting slogans against "dictatorship".

All these four youths have been arrested along with Jha, who surrendered before the Delhi police last week, and the friend he had allegedly visited in Nagaur, Mahesh Kumawat.

Police sources said Jha had, with Kumawat’s help, destroyed the mobile phones of the four other accused.

Jha, a Calcutta resident and a teacher by profession, and the other five accused have been booked under the anti-terror law UAPA and various IPC provisions.

All six are in Delhi police custody. So far, the police have not found any evidence linking them to any terror group, sources said.

“During interrogation, the accused said their objective was to draw Prime Minister Narendra Modi’s attention to the problems of unemployment and the situation in Manipur. But we are probing all angles,” a police officer who is part of the probe told The Telegraph.

While D. Manoranjan and Sagar Sharma had jumped into the Lok Sabha chamber from the visitors’ gallery with smoke canisters hidden in the soles of their shoes, Neelam Azad and Amol Shinde had protested outside Parliament, also with coloured smoke.

Jha had allegedly shot videos of the protest by Azad and Shinde, posted them on social media and sent them to an acquaintance in Bengal seeking media coverage, before fleeing to Rajasthan.