The Pakistan High Commission staffer, who was detained for his alleged involvement in an espionage ring, belongs to the Baloch regiment of the Pakistani Army and was on deputation to the Inter-Services Intelligence, Pakistan's spy agency, since 2013.
Investigators probing the case suspect more people from the mission may be involved in the espionage ring.
Sources in Delhi Police also did not rule out possible involvement of some Border Security Force personnel in the racket as they believe the staffer Mehmood Akhtar and his accomplices could not have got hold of deployment details unless somebody in the BSF was leaking them.
Akhtar, who worked in the visa section of the Pakistani high commission, had procured sensitive defence documents and deployment details of BSF along the Indo-Pak border and shared them with the ISI. Two of Akhtar's accomplices were already arrested.
Akhtar was detained but released after prolonged questioning as he enjoys diplomatic immunity.
He said that he is on deputation to ISI since January 2013 and is a serving Hawaldar of 40 Baloch Regiment of Pakistan army and native of village Kahuta of Rawalpindi district, said Ravindra Yadav, joint commissioner of police (Crime).
During the interrogation, Akhtar said that he was posted in Pakistan high commission for last two-and-a-half years.
It is also suspected that he lured many people into the spying ring by offering them good money and that there was a honey trap at play to lure people, said another officer in the probe team.
Sources said more people in the Pakistani high commission may be involved in the case.
On possible involvement of BSF personnel, they said, "The documents that were recovered from them couldn't have been procured without the help of someone privy to such sensitive information. We are suspecting that they were aided by some BSF personnel who leaked the information and documents to them.
"We are investigating that aspect. We have identified some of the officers involved and we will be conducting a raid soon."
The Delhi Police had been tracking the module for the last six months and received information on October 25 that Akhtar will be meeting Subhash Jangir and Maulana Ramzan at the Delhi Zoo on October 26 around 10 am, said the officer.
A team of officers of Crime Branch led by ACP Sanjay Sherawat under the supervision of DCP Crime (South) Bhisham Singh laid a trap and caught the trio while they were in the process of exchanging documents.
Akhtar initially showed an Aadhar card in the name of Mehboob Rajput.
"He claimed to be a resident of Chandni Chowk but after sustained interrogation, he revealed his real name Mehmood Akhtar," said Yadav.
He was carrying a forged Aadhar card to assume an Indian identity. "He is serving with Pakistan ISI and has got diplomatic immunity since he is posted in the Pakistan High Commission of Delhi. This was verified through MEA and after confirmation and as per the due procedures, he was handed over to the PHC diplomats in presence of MEA representative," Yadav said.
Since Akhtar was working in the visa department, it gave easy access to him to identify people who could work for him as spies.
"He would chat up with people about their family background and then start laying his trap. People who were financially weak would be lured by promise of getting big money," said a senior police officer. The officer said the honey trap angle was also being explored.
"From initial investigation, it has been revealed that some girls were exploited after being promised good money and were used to lure men into the module. We are investigating this aspect," he added.
Police has also recovered the mobile phones of Maulana and Jangir, who were sharing information and documents with Akhtar.
"It has been found that they used to mostly communicate through whatsapp calls as they are not recorded. We cannot procure the call detail records of calls made through whatsapp.
"On normal phone calls, their conversations would mostly happen through codewords and we were studying the pattern in the last six months," said a senior police officer.
Akhtar would meet Maulana and Jangir once every month in Delhi where they would give documents to him and he would pay them a high amount in return.
During interrogation, they didn't reveal the amount for leaking information but it is suspected to be in the range of Rs 30,000-Rs 50,000, said a senior police officer.
Akhtar had come in contact with Maulana and Jangir through a Jodhpur-based passport and visa agent, identified as Shoaib.
Maulana and Jangir are residents of Nagaur in Rajasthan. Maulana has been working as an Islamic preacher at a local mosque Qureshiyon ki Masjid there and Subhash had a small kirana shop near the mosque.
Ramzan was in contact with Shoaib, who is yet to be arrested.
Subhash incurred huge losses in business and Ramzan asked him to become a part of the module.
Image: Pakistan High Commission in New Delhi. Photograph: Reuters