A Pakistani militant group apparently used an Indian operative as far back as 2007 to scout targets for the elaborate plot against India's financial capital, authorities said Thursday, a blow to Indian officials who have blamed the deadly attacks entirely on Pakistani extremists. As investigators sought to unravel the attack on Mumbai, stepping up questioning of the lone captured gunman, airports across India were put on high alert amid fresh warnings that terrorists planned to hijack an aircraft. Also Thursday, police said there were signs that some of the six victims of the attack on a Jewish center may have been strangled. "The victims were strangled," said Rakesh Maria, a senior Mumbai police official. "There were injuries noticed on the bodies that were not from firing." Members of an Israeli rescue group, which had a team in Mumbai, said it was impossible to tell if the bodies had been abused, however, because no autopsies were conducted in accordance with Jewish tradition. The surviving gunman, Ajmal Amir Kasab, 21, told interrogators he had been sent by the banned Pakistani militant group Lashkar-e-Taiba and identified two of the plot's masterminds, according to two Indian government officials familiar with the inquiry. Kasab told police that one of them, Zaki-ur-Rehman Lakhvi, Lashkar's operations chief, recruited him for the attack, and the assailants called another senior leader, Yusuf Muzammil, on a satellite phone after hijacking an Indian vessel en route to Mumbai. The information sent investigators back to another reputed Lashkar operative, Faheem Ansari, who they hope could be key in pulling together different strands of the investigation. Ansari, an Indian national, was arrested in February in north India carrying hand-drawn sketches of hotels, the train terminal and other sites that were later attacked in Mumbai, said Amitabh Yash, director of the Special Task Force of the Uttar Pradesh police. During his interrogation, Ansari also named Muzammil as his handler in Pakistan, adding that he trained in a Lashkar camp in Muzaffarabad - the same area where Kasab said he was trained, a senior police officer involved in the investigation said. In Pakistan, Interior Ministry chief Rehman Malik told reporters he had no information on Lakhvi or Muzammil but that authorities would check. Ansari "told us about a planned Lashkar attack on Bombay, on southern Bombay," said Yash, referring to Mumbai by its previous name. "He gave us eight or nine specific locations where the attack would be carried out," he said, adding that Ansari had detailed sketches of the places and escape routes from the sites. Ansari said he carried out the reconnaissance in the fall of 2007, which also included the US consulate, the Bombay stock exchange and other Mumbai sites that were not attacked. Ansari is now in Indian custody, according to Yash. It was unclear if he was being questioned again, but Maria said they were working to determine if Ansari played a role in how the attackers "got such intricate knowledge of the sites." Indian authorities have faced a torrent of criticism about missed warnings and botched intelligence, and revelations that Ansari disclosed details of the Mumbai plot 10 months ago will be added to the list. Linking an Indian national to the plot also undermines India's assertion that Pakistan is solely responsible. Yash said during extensive interrogations Ansari confessed to scouting Mumbai, arranging a safe-house there for Lashkar militants and provided details on his involvement in the group. "We got everything out of him, whatever he knew," he said. Ansari linked up with Lashkar while working at a printing press in Dubai. He was taken by sea to Pakistan to the Lashkar camp in Muzaffarabad and received a false Pakistani passport and citizenship papers, which police recovered when he was arrested. In 2007, Ansari said, he traveled to Katmandu, Nepal, and then crossed back into India and settled in Mumbai, where he conducted reconnaissance for a future attack, Yash said. He was arrested Feb. 10 in the northern city of Rampur after suspected Muslim militants attacked a police camp, killing eight constables. He said he was there to collect weapons to bring to Mumbai for a future attack. Yash said Ansari's arrest did not derail Lashkar's plans for an attack. "When they found that their mole in Bombay had been caught ... they carried out the operations in a different way," he said. Meanwhile, police officers said they were trying to get as much detail as possible from Kasab. "A terrorist of this sort is never cooperative. We have to extract information," said Deven Bharti, the head of the Mumbai crime branch. Indian police are known to use interrogation methods that would be regarded as torture in the West, including questioning suspects drugged with "truth serum." Bharti provided no details on interrogation techniques, but said "truth serum" would probably be used next week. He did not specify what drug would be used. During questioning, details of Kasab's recruitment by Lashkar began to emerge, said police, describing him as fourth grade dropout from an impoverished village who was gravitating to a life of crime. "Lashkar recruited him, preying on a combination of his religious sentiments and his poverty," said Maria. The revelations came as US Secretary of State Condoleezza Rice met with leaders in Islamabad after visiting India's capital - part of a US effort to pressure Pakistan to share more intelligence and pursue terrorist cells believed to be rooted in the country. Pakistani President Asif Ali Zardari promised Rice his country would take "strong action" against any elements in Pakistan involved in the siege. On Thursday, the US Treasury Department designated as terrorists four individuals who hold leadership positions in Lashkar, including Lakhvi, and ordered any of their US assets to be frozen. Also named were Muhammad Saeed, the group's leader; Haji Muhammad Ashraf, its chief of finance; and Mahmoud Mohammad Ahmed Bahaziq, a financier with the group. Meanwhile, India put its airports on alert following threats of possible airborne attacks. Security forces swarmed New Delhi's international airport early Friday after the sound of gunfire was heard, police said, but no one was injured or killed. Police said it was not a terrorist incident. The warning received by the airports "spoke of possibility of aircraft being hijacked by terrorists," India's air force chief, Fali Homi Major, told reporters Thursday. The alert focused on three major airports - New Delhi, Bangalore and Chennai - but security was stepped up across India. Several extra layers of security were set up and some passengers' bags were scanned for explosives. "Passengers have been asked to pass through six-stage security checks," said Brij Lal, a senior police official organizing security at the airport in the northern city of Lucknow. Nirmala Sharma, a passenger who flew from New Delhi to Lucknow, said her bags were checked a half dozen times and she went through a metal detector three times. "Sometimes it seemed tedious, but it seems to be the need of the hour," she said.