Pakistani investigators, meanwhile, remain clueless about the attacks despite arresting five Afghan refugees in this connection.

The FBI team, the strength of which was not known, is expected to interact with the Pakistani army, police experts and professionals from the bomb disposal squad to find clues into the attacks, the Nation said quoting sources.

One security guard at the American centre was injured, a number of vehicles destroyed and minor damages were caused to the property following the attacks. Meanwhile, the local police has constituted a joint investigation team to examine the attacks but is yet to come out with any definite evidence. Police, however, has rounded up five Afghan refugees from different parts of Islamabad and is interrogating them in a bid to reach to some conclusion, the largest circulatedUrdu daily Jung said quoting police sources.

A number of Pakistani intelligence agencies are also helping the local police in finding a lead into the attacks.

The police, however, has managed to identify at least two of the vehicles used for the rocket attacks but both the vehicles have turned out to be stolen some time ago and had false number plates on them.

The rockets were fired from locally made rocket launchers fitted into the vehicles which caught fire as soon as the rockets were fired apparently by some remote controlled device.

The police has also sought the assistance of a team of the defence production division which is examining the rocket launchers and a couple of unexploded rockets to determine their origin.

Jung said that the rocket launchers were of the same type as those found when a major arms depot at Ojhri in the outskirts of Islamabad had caught fire about 11 years ago. The Pakistan Observer quoting local sources claimed that the investigations suffered a setback when theAmerican embassy here refused access to the police to the video recording of the cameras installed around their embassy building and American Centre.

Meanwhile, security in the Capital continued to be tight with authorities banning pillion riders on motorcycles as well use of tinted glass on cars.Incidentally, some Pakistan based religious groups had been threatening US since August for pressing the Taliban government in Afghanistan to hand over Saudi terrorist Osama bin Laden.