Washington ? American authorities investigating the killing last year in Pakistan of Wall Street Journal reporter Daniel Pearl now believe his throat was slit by Khalid Shaikh Mohammed, the alleged mastermind of the Sept. 11 terrorist attacks.

Authorities, who had previously cast doubt on reports alleging Mohammed’s role, have new information that leads them to believe he killed Pearl, said a U.S. official who spoke on condition of anonymity. The official would not detail the evidence.

However, some senior Pakistani officials involved in the Pearl case said Tuesday they could not confirm suspicions that Mohammed was Pearl’s killer.

There had been suspicions in Pakistan that Mohammed was involved in Pearl’s kidnapping and murder last year and may even have killed the correspondent.

“Many newspapers have been reporting it. We do not have evidence or credible information,” said an official with the Pakistani intelligence service, who spoke on condition of anonymity.

Investigators obtained videotapes that apparently showed Pearl being killed as his throat was cut, but it was unclear from the pictures who killed him. Additional footage showed his body being decapitated.

Pearl’s body was found in May last year.

Mohammed was captured March 1 in Rawalpindi, Pakistan. The CIA is interrogating him at an undisclosed location. He is believed to have been among al-Qaida’s most senior, and successful, operational masterminds.