NEW DELHI, India (CNN) -- An FBI agent Wednesday testified in the Mumbai terror trial, Indian prosecutors said.
The officer, whose identity has not been revealed, testified via videolink, chief public prosecutor Ujjwal Nikam told CNN.
The agent told Mumbai's prison court that his investigation of the data from the global positioning systems seized after the attacks showed the gunmen traveled down to the Indian financial hub from Pakistan's port city of Karachi.
Nikam said he would be examining two more FBI agents in the next two days through video conferencing.
Two other U.S. nationals will also testify in person after that, he said.
The defendant, Mohammed Ajmal Kasab, stunned the court in late July when he changed his plea and confessed to taking part in the attack that killed more than 160 people in India's financial capital.
Prosecutors said Kasab's guilty plea was an attempt to deflect attention from his alleged handlers in Pakistan. Kasab is a Pakistani national.
Nikam told the court he needed to examine more witnesses to shed light on why foreign nationals, among others, were targeted in the November siege.
The judge in the case ruled the trial would continue despite Kasab's plea and said the court will take up Kasab's confession at a later date.
"He has changed his stance repeatedly. So I have requested the court that he is operating on an ulterior motive and that the trial should continue," Nikam told reporters.
Kasab has told the court he is ready to face execution.
Prosecutors said they will hold off on recommending a sentence because Kasab has not disclosed more about what he knows about the planning and execution of the attack.
Kasab is the only survivor out of 10 Pakistani nationals who launched the attack, laying siege to buildings such as the Taj Mahal Palace and Tower and Oberoi-Trident hotels, Mumbai's historic Victoria Terminus train station and the Jewish cultural center, Chabad House. The other nine were killed.
The attack began on November 26 and continued for four days and three nights.
Authorities said Kasab was trained by Lashkar-e-Tayyiba, a militant group that was banned in Pakistan in 2002 after an attack on India's parliament. The group denied responsibility.