Another two Interpol experts -- American Marash Vucilaj, a specialist on public safety and security, and Chinese Xin Hu, an expert on terrorism -- also flew in the capital around 12:30pm to probe the grisly attack.

They met officials of the intelligence agencies and gathered primary information on the deadly incident and are scheduled to start investigation today.

Earlier, a two-member advance team of Interpol on Tuesday sent a preliminary assessment report to its headquarters in Lyon, France.

Gibson Wilson, an FBI forensic expert, started probing the incident after arriving here early yesterday.

But foreign ministry officials continued to rule out the possibility of US involvement in the investigation until yesterday. But an high official of the US Embassy in Dhaka, speaking on condition of anonymity, said the FBI official has come after Bangladesh government sought US assistance in the ongoing investigation.

The official did not disclose the time of arrival of Wilson neither would he say how long the FBI official will stay in Bangladesh. He, however, confirmed that Wilson is a special agent of the FBI having expertise in forensic.

The US embassy also confirmed yesterday that Counter-Terrorism Coordinator of the US State Department Cofer Black is set to arrive in Dhaka on Sunday.

Black, a former CIA (Central Intelligence Agency) official, is responsible for US efforts to improve counterterrorism cooperation with foreign governments and plays a leading role in the State Department's taskforces to coordinate responses to international terrorist incidents.

Wilson talked with the officials of local intelligence agencies and visited Sudha Sadan, the Dhanmondi house of Hasina, also the AL president.

During the over-two-hour visit to Sudha Sadan, Wilson examined the bulletproof sports utility vehicle of Hasina, which was riddled with bullets and grenade shrapnel while carrying her to safety, in the presence of her political secretary Saber Hossain Chowdhury.

Officials of the National Security Intelligence (NSI), Criminal Investigation Department (CID) and Directorate General of Forces Intelligence (DGFI) accompanied Wilson during the visit at around 2:30pm. Regional Security Officer of the US Embassy in Dhaka David Motley also accompanied him.

The FBI official examined the nature of damage to the vehicle, took snaps and collected evidence. The FBI will analyse the evidence and prepare a report on the basis of the evidence. However the FBI official did not talk to reporters who gathered at Sudha Sadan.

Saber told waiting journalists that the FBI and intelligence officials went to Sudha Sadan to make forensic and ballistic examinations of Hasina's bullet-hit vehicle. He said the AL is only extending its cooperation in the investigation.

"The vehicle would have been better evidence if it had been examined instantly," Saber said.

The FBI is responsible for protecting the US and its citizens from future terrorist attacks. The responsibilities include upholding the law through the investigation of terrorists and terrorist-related activity and protecting the US from foreign intelligence activities.

Investigating violations of federal criminal law and providing leadership and law enforcement assistance to federal, state, local and international agencies are also FBI's tasks.