The two persons who opened smoke canisters in the Lok Sabha chamber had smuggled them in cavities cut into the left sole of custom-made sports shoes supported by thick rubber layers, according to Delhi Police's FIR.
The pamphlets that the duo -- Manorajan D and Sagar Sharma -- carried into the Lok Sabha had the picture of a fist against the backdrop of a tricolour, a slogan in Hindi and a slogan in English on the Manipur violence issue.
In a major security breach on the anniversary of the 2001 Parliament terror attack, Sagar and Manoranjan jumped into the Lok Sabha chamber from the public gallery during Zero Hour on Wednesday, released yellow gas from canisters and shouted slogans before being overpowered by the MPs.
Around the same time, two others -- Amol Shinde and Neelam Devi -- sprayed coloured gas from canisters while shouting "tanashahi nahi chalegi" outside Parliament premises.
Police have filed terrorism charges under the stringent UAPA against the four people.
According to the FIR, the smoke canisters, which were opened inside and outside Parliament, had warnings and instructions to "wear goggles and gloves" while opening.
A cavity was cut into the left sole of the LCR-made grey coloured sports shoes of Sagar Sharma. The thickness of the soles was increased by affixing additional rubber to support the cavity, it stated, adding that Manoranjan D's sports shoes too had a similar cavity in the left sole.
Police said the right sole of the shoe was also found partly cut.
The police registered the FIR at the Parliament Street police station based on a complaint filed by a police staffer.
"I along with inspector Vinay Kumar, officiating SHO PS Parliament Street, and other staff reached the office of the director of security of the new Parliament House Building where Omkar Singh, Deputy Director(S) Lok Sabha was present.
"He handed over the complaint along with aforesaid mentioned persons namely Sagar Sharma and Manoranjan D. He also handed over shoes of both the alleged and their Aadhar cards," the FIR stated.
Police said the other two accused -- Amol Shinde and Neelam -- were nabbed with four used and an unused coloured smoke canister. All these canisters bore a reminder to the users to wear goggles and gloves and never use those in indoor or enclosed spaces, they said.
Earlier in the day, the Delhi Police Special Cell questioned two more persons in connection with the Parliament security breach case, an official source said on Thursday.
The police's Special Cell's Counter Intelligence unit picked up two persons, including one from Rajasthan, on Thursday night. They had allegedly helped Lalit Mohan Jha -- thought to be the brain behind the security breach plan -- go into hiding after the incident, a source said.
Jha, who had been on the run after the incident on Wednesday, walked to a police station in the New Delhi district on Thursday night and is now being interrogated by a counter-intelligence team, a source said.