An investigation into the security breach in Parliament will review lapses not only by Delhi Police and paramilitary forces but also the Parliament Security Service (PSS), a specialised department primarily tasked with safeguarding the entire complex, officials aware of the details said on Thursday.

On Wednesday, two people managed to clear multiple layers of security, smuggled smoke canisters into the Lok Sabha, and jumped into the House from the visitor’s gallery; two others protested outside the building with similar gas canisters and shouted slogans.

The suspects, investigators said, hid the canisters in their shoes, uncovering glaring gaps in the Parliament’s security machinery.

The security breach – the gravest since the December 2001 terror attack two decades ago – triggered protests and led to the suspension of eight security personnel on Thursday.

“Investigators will not only probe the lapses by Delhi Police and paramilitary forces but also the PSS that is largely responsible for the security inside the complex,” an official aware of the details said.

Headed by a joint secretary (security), usually the rank of an inspector general, PSS is an independent, specialised department that monitors the security of the interiors of Parliament House. The outer perimeter is manned by paramilitary jawans, the area surrounding the complex is protected by Delhi Police.

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The 930-personnel strong PSS – which reports to the Lok Sabha – is largely entrusted with monitoring the security checks and entry of visitors.

A senior Delhi Police officer said the PSS joint secretary is aided by two directors (security) of Lok Sabha and Rajya Sabha respectively. These directors are usually deputy inspector general (DIG)-rank officers who come on deputation from the paramilitary forces.

However, the joint secretary post has been vacant since Indian Police Services (IPS) officer Raghubir Lal was transferred to Uttar Pradesh Police on November 2.

Besides the two directors, the officer explained, the PSS is also assisted by a large contingency of personnel from the Central Reserve Police Force (CRPF). Personnel from both are together known as the Parliament Duty Group (PDG), which remains guard at the periphery of and within the complex to thwart any intrusion. The head of the PDG – a DIG rank officer – also reports to the joint secretary.

“While the joint secretary and directors of Parliament Security Service are police officers, all other personnel such as security assistants (Grade I, Grade II), security officers and dog handlers are hired by the recruitment cell of Parliament. These recruits are not police officers. They do not wear a uniform and also do not carry arms. These personnel are in-charge of the ward and watch duties,” the officer, who has served in the New Delhi district, said on condition of anonymity.

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“They (PSS personnel) are posted at the gates of Parliament and check the identity of visitors, frisk them and allow or reject entry. The idea behind having PSS employees on the ward and watch duty (also called access control) is because it is assumed that PSS employees know the identity of all parliamentarians,” the officer added.

At the main gate of Parliament, PSS officers are assisted by Delhi Police, the officer said. “When a session is underway, the Speaker’s office requests Delhi Police to send its personnel, who are then posted at the iron gates along with PSS personnel to frisk visitors,” the officer said.

A former CRPF officer, who has in the past served in the PDG, explained the deployment of the PSS.

“PSS is posted at all the three gates, i.e. main iron gate (gate 1), entrance of the building (gate 2) and entrance of the visitor or other gallery (gate 3). They guard the baggage scanners and check the passes carried by visitors. CRPF personnel of the PDG stand next to them to see there is no forced intrusion,” the officer said, also seeking anonymity.

The officer said that as per Parliament’s standard operating procedure, the PSS has to alert their control room in case of any intrusion. The control room, in return, will alert the armed paramilitary forces and Delhi Police.

The area outside the Parliament gate is manned by the CRPF and Indo-Tibetan Border Police