NEW DELHI: The voice had long haunted Indian police investigating Mumbai's deadly 2008 terrorist attack.
They had repeatedly listened to a tape of cell phone intercepts containing chilling words from one of the men guiding 10 terrorists through the gun-blazing rampage that killed 166 people in India's financial capital.
''Pass this message to the media—‘this is just the trailer; the real film is yet to come,''' the voice said.
Anti-terror police engaged in one of India's largest investigations had no idea who the man was, only that he had a Mumbai accent and used Hindi words unusual for Urdu speakers like the attackers on the ground.
Police believe they finally have the man behind the disembodied voice after ferreting out the suspect from Saudi Arabia where he was hiding, according to officials close to the investigation. They say he had given himself away to the police by opening a Facebook account under his real name—Syed Zabiuddin Ansari.
Ansari—an Indian citizen whose aliases include Abu Humza, Abu Jindal and Abu Jundal—was arrested at New Delhi airport on June 21 after Saudi Arabia agreed to hand him to Indian officials and put him on a flight home.
Indian investigators told The Associated Press that Ansari was considered a key player in the plans for attacks on India. They say he was so central to the Mumbai attack plans he was among those giving orders by the minute to the attackers or directing them on their cell phones from a control room in Karachi, Pakistan during the Nov 26-28 bloodbath.
The investigators spoke on condition of anonymity because they were disclosing sensitive information.
Ansari's interrogation is expected to bolster the Indian government's accusations — and accepted as a fact by most ordinary Indians — that Pakistan was behind the attack, the most brazen terrorist operation on India's soil.
His arrest is a rare piece of good news for a government reeling from economic and political troubles.
''Clearly there was state support for the 26/11 massacre,'' Home Minister Palaniappan Chidambaram said Friday.
Indian investigators say Ansari has already told them that Pakistani intelligence officials were in the control room during the 60-hour siege — corroborating testimony by American terrorist suspect David Coleman Headley, who said during his Chicago trial last year that Pakistani intelligence officials were involved.
Ansari has also told investigators he fled India in 2006 across the border to Bangladesh, escaping from a police raid in the western Indian town of Aurangabad on an illegal cache of weapons and explosives intended for future attacks within India, the officials said.
The assault was like no other India had experienced. Bombs and grenades went off at the famed Taj Mahal and Trident hotels. Then, 10 trained militants fanned out through the hotels and through the main train station and a Jewish cultural centre and gunned down people in their paths.
The attack went on for three days, as Indian police scrambled to keep up with the militants who were receiving detailed instructions by cell phone.
Eventually all but one of the gunmen were killed.
The survivor, Ajmal Kasab, told a special Indian court he and the others were tutored by a man named Abu Jindal on how to speak with a Hindi accent to avoid detection in India and confuse police about their origins.
Police are now looking for a second man who is heard on the tape from the control room. That man, who police believe is Muzammil Butt, based on testimony from other suspects, is heard cutting the attackers off as they exclaimed about the size of the television screens and the luxury fittings in the five-star hotels.
At one point, he is heard saying: ''How hard is it to throw a grenade? Just pull the pin and throw it.''
Investigators had been looking for Ansari for years after he was implicated by other suspects in the Mumbai attacks, but they never knew his exact role in the attack, said officials close to the investigation.
India learned Ansari was living in Saudi Arabia on a Pakistani passport, officials said.
Both India and Pakistan then began lobbying for his release into their custody, but India clinched the arrest by providing DNA samples from Ansari's Indian family members, who live in the western state of Maharashtra, where Mumbai is located, the officials said.
Intelligence agents are now interrogating Ansari in a secret location on the outskirts of New Delhi.
Ansari told Indian investigators he had gone to Saudi Arabia to raise funds and recruit more Indians as militants. Investigators say militant groups routinely try to recruit Indians from among the two million Indians living in Saudi Arabia or the millions who visit the country to perform the Haj.
He might have remained in the shadows had he not opened a Facebook account in his real name to find new recruits, the officials said. The Times of India reported last week that Ansari also used the account to contact accomplices, who may have been under global scrutiny by intelligence agencies.
Indian investigators followed his electronic trail to Riyadh, and this week used voice recognition tests to match Ansari's voice with the man on the tape. While the Hindi he spoke is similar enough to Urdu that speakers understand each other, there are many words that differ.
The man recorded giving instructions to the attackers used a few Hindi words an Urdu speaker would not use, such as "prashasan" for "administration," officials said. The Urdu word would be "intizamiya."
Investigators have sent the voice samples to a lab for further analysis, newspaper reports said.
Saudi Arabia's decision to hand Ansari over to India, rather than Pakistan, appeared to surprise Indian officials.
Foreign Ministry spokesman Syed Akbaruddin described the arrest as something "rather new" in Saudi-Indian relations.
"Our relationship with Saudi Arabia is expanding in a variety of ways."
Analysts said Riyadh's decision marked a significant shift.
"It is a signal to Pakistan that it will get isolated if it thinks state sponsorship of terrorism can be a viable policy option," said Ajit Doval, former chief of India's Intelligence Bureau.