Sources privy to the investigations of the terror suspect's trail in India said 48-year-old Headley was very much present in the room from where the ten LeT terrorists were being guided to various locations during the 26/11 attacks.
The investigators re-visited the intercepts and found that there were specific instructions being given to terrorists about entry and exit, including that they had taken more time before reaching their final targets, which included the Taj Mahal hotel, Oberoi and Trident towers and Nariman House.
India has asked for a voice sample of Headley from the Federal Bureau of Investigation to match with a voice which was unidentified so far for the security agencies.
This voice was giving information on exact surroundings of the targets attacked by the Lashker-e-Tayiba militants. However, there was no firm response from the FBI on providing the same to the Indian investigators, the sources said.
The sources claimed that there were frequent promptings done by Headley to Lashker-e-Tayiba mastermind Zaki-ur-Rehman Lakhvi from a room in Pakistan.
Lakhvi, against whom the Interpol has issued a Red Corner Notice at the request of India, was in turn touch with the terrorists attacking Mumbai.
Headley, who has visited India nine times - eight times before 26/11 and once in March this year -- had conducted recce of Nariman House, Taj Mahal hotel, Lepold Cafe, Chatrapati Shivaji Terminus and Oberoi-Trident hotels.
He had conducted a detailed recce of Nariman House before the Mumbai carnage and even entered the targeted Jewish Centre posing as a Jew.
National Investigation Agency had recorded statements of some of the witnesses who had either seen or accompanied Headley to Nariman House, also known as Chabbad House.
Six of the occupants including Rabbi Gavriel Noach Holtzberg and five-month pregnant wife Rivka were killed by the Lashkar militants.
The two-year-old son of Rabbi -- Moshe -- was saved by his nanny Sandra Samuel. The attack by LeT terrorists last year in the five-storeyed house, which can be approached only through narrow lanes and by-lanes of Colaba, had left the security agencies without any doubt that a proper recce had been conducted before the strike.
A proper communication had also been ensured so that the terrorists attacking the Jewish centre did not get confused within the by-lanes leading to the Nariman House, the sources said, adding there is evidence that Headley was there in the room when the terrorists were raining bullets in the city.
Headley, who is now facing FBI charges of conspiring in the 26/11 attacks, had used the service of many prominent individuals in the city to conduct a proper recce of the places which also included the Bhaba Atomic Research Centre, Israeli Embassy in Cuffe Parade and Israeli airlines office located in the World Trade Centre.
Headley had stayed at the Oberoi for four days in April last year despite staying as a paying guest in Mumbai and before that in Taj Mahal.
He had later left India reportedly for Pakistan through a Gulf country.
Investigators, probing the terror links of Headley had found that the suspects was moving freely in Pakistan, from where the Mumbai attackers had come and unleashed bloodbath in the megapolis for four days.
More than 20 teams of sleuths of NIA, a prosecuting agency established in the aftermath of 26/11, have been entrusted to probe Headley trail and central security agencies have been formed for gathering information about the places Headley and his associate Tahawwur Rana had visited between 2006 and 2009.
NIA has booked Headley and Canadian-Pakistani Rana under Unlawful Activities Prevention Act for conspiring to wage a war against the country.