India is investigating whether a Chicago man accused of helping plan the deadly 2008 Mumbai siege was a double agent working for the United States and a Pakistan-based militant group, an official said on Wednesday.
"India is looking into whether (David Coleman) Headley worked as a double agent. That is one of the many angles we are probing," a home ministry official said following a flurry of local media speculation.
Headley, 49, a Pakistani-American, was arrested in October and has been charged in a Chicago court with conspiring to bomb public places in India and of aiding and abetting the murder of US citizens in India.
The Indian government, led by the Congress party which has made closer US ties the keystone of its foreign policy, is already under pressure from the opposition over the case.
Indian media reported that New Delhi was suspicious because the United States had not shared vital information about Headley's movements prior to his arrest.
There are also doubts about how Headley funded an apparently lavish lifestyle while living in Mumbai, leading Indian investigators to scrutinise his American credit card bills, the press reported.
The Times of India quoted an unidentified official as saying it was "very strange" Washington failed to inform New Delhi about Headley's visit to India in March this year, "when he, by their own account, had been under their surveillance since at least September 2008."
The Daily Mail quoted an unidentified official as saying that the American Central Intelligence Agency (CIA) had not shared information with New Delhi "apparently to ensure that Headley did not get exposed as a US secret agent."
The Washington-born son of a former Pakistani diplomat and American mother, Headley reportedly made a number of trips to India over the past few years visiting many places including Mumbai and befriending Bollywood stars.
The Times suggested that Headley could have been a member of the US Drug Enforcement Agency which allowed him to make frequent trips to Pakistan and gain access to the Lashkar-e-Taiba (LeT) militant group.
Headley was arrested for heroin smuggling in 1998 in New York, according to reports, which was when he is alleged to have been recruited by the DEA.
India blames the LeT for planning and executing the Mumbai siege in November 2008 when 10 gunmen targeted multiple locations in the commercial capital, killing 166 people including six Americans.
India's home secretary Gopal K. Pillai has said the government would seek Headley's extradition to aid its investigations.
Headley could face the death penalty if convicted of all 12 charges laid against him in Chicago.