BEIRUT - Visiting U.S. Under Secretary for Political Affairs David Hale says the Federal Bureau of Investigation will be joining Lebanese and other international investigators in the probe into the Beirut port blast that killed and wounded thousands.Hale said during a visit to one of the impacted neighborhood in Beirut on Thursday that the FBI will take part at the invitation of Lebanese authorities.He said the participation in the probe is one of the ways the US is helping Lebanon in dealing with the aftermath of the drastic explosion.