Washington, US’ Federal Bureau of Investigation (FBI) will join Lebanese and other international investigators to probe what caused the explosion at Beirut’s port that killed more than 170 people and injured thousands while causing widespread destruction, a US diplomat said on Friday.”The FBI was invited by the Lebanese authorities to join in the investigation, and it is one way that Washington can help the country deal with the effects of the disaster”, said US Under Secretary for Political Affairs David Hale after he toured the Gemmayzeh neighbourhood, which was damaged by the August 4 blast.The FBI will be joining Lebanese and other international investigators from countries like France in order to find out what caused this explosion, Al Jazeera reported.On 4 August, 2,750 tons of ammonium nitrate stored at Beirut’s port blew up, obliterating the city’s main commercial hub and damaging large swathes of the Lebanese capital. The blast, the most destructive in the country’s troubled history, killed more than 170 people, wounded more than 6,000 and caused damage worth $10bn-$15bn.