The Federal Bureau of Investigation (FBI) registered a case in connection with the audacious Mumbai serial attack that left over 180 people, including six Americans, dead and are helping Indian investigators in cracking codes of Internet telephony used by terrorists of Lashker-e-Taiba.

The FBI team, accompanied by investigators from Scotland Yard, are camping in Mumbai for the last two days collecting information. They are also assisting the Internet telephony signatures intercepted by Indian intelligence agencies when militants were receiving calls from their Lashkar handlers from across the border.

The FBI team, which came here on Sunday, was attempting to decode the Internet telephony.

As per the US laws, the FBI has to probe the death of any American citizen outside of the US and later submit a charge sheet. In this case, it sought the interrogation report of Mohammad Ajmal Amir Iman who was arrested by police on November 26 from Chowpatty area.

The FBI was trying to ascertain the origin of the mail and how many times it was opened in Pakistan. The deciphered packets of the satellite conversation between the militants and their handlers, and the air length frequency waves used for conversing on Internet were also being examined.