New Dehli, India ? 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, 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 tortured. “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.