The U.S. State Department announced it was offering a $5 million reward for information about the location of Taliban leaders Hakimullah Mehsud and Wali Ur Rehman, believed to be hiding in northern Pakistan.
Anonymous U.S. government officials told CNN in February that Mehsud died from wounds suffered during a Jan. 14 airstrike in North Waziristan. Pakistani officials said his body was buried in late January.
The Long War Journal, an Internet publication monitoring the conflicts in Afghanistan and Pakistan, however said it received two tapes from the Pakistani Taliban dated in April showing Mehsud was alive.
The State Department describes Mehsud as the leader of the Pakistani Taliban, blaming the terrorist leader for a December suicide operation on a CIA base in Afghanistan that left seven U.S. citizens dead.
The Pakistani Taliban claimed responsibility for a failed bombing attempt on Times Square in New York City in May, though local authorities at the time downplayed the claims.
Rehman is believed to be the second-in-command of the Pakistani Taliban and a top military strategist. The State Department said he led several attacks on U.S., NATO and Pakistani forces fighting in the area.
Ronald Machen, the U.S. attorney for the District of Columbia, said in an FBI statement regarding the two militant leaders that Washington would use "every tool" available in the pursuit of justice.
"We have no higher priority than bringing to justice terrorists who kill Americans serving and working abroad," he said.