Suspected American terrorist David Headley had stayed in a hotel in the national capital just months before the 26/11 attacks in Mumbai.
According to the passport details of Headley, he had visited the national capital and Mumbai during April last year. He had then left for Pakistan.
Headley was arrested by the FBI for suspected links with the banned terror group Lashkar-e-Taiba, which had carried out the Mumbai carnage last year that left about 180 people dead.
Sources said Central security agencies are also investigating Headley's suspected links to terror outfit Indian Mujhaideen, which had carried out a series of bomb attacks across the country, including in Rajasthan and Delhi, that left over 170 people dead.
Home Minister P Chidambaram had said on Thursday that besides Headley, the National Investigating Agency had registered a case against his Canadian accomplice Tahawwur Hussain Rana.
The duo was booked under the Unlawful Activities (Prevention) Act and for conspiring to wage war against the country.
Maintaining that Headley had visited India several times before 26/11 and once after the Mumbai terror strikes, Chidambaram had said, "We are conducting investigations in the cities he visited to find out whom he met and what he did."
The Mumbai attack last November left 183 persons dead. A top Home Ministry official has claimed that the investigators had enough evidence to show Headley's link with LeT and the Government is all set to produce the documents before a US court in January next and press for his extradition to India.
"We will press for his extradition to India with the evidence," the official said. The investigators were now trying to find out whether Headley and his accomplice Rana, also arrested in the US, were involved in the 26/11 attacks in Mumbai and whether handlers of the duo and Mumbai attackers were the same.