The US Federal Bureau of Investigation said on Tuesday that it had reached no firm conclusion about what caused the August 4 explosion in the port of Beirut that killed about 190 people and caused billions of dollars in damage. Other US and European government agencies following the investigations into the explosion strongly believe that the blast was an accident. "No such conclusion has been reached," an FBI spokeswoman said. She cited an earlier statement in which the US agency said it would be "providing our Lebanese partners investigative assistance". "Further questions should be directed to the Lebanese authorities as the lead investigators," she said. Lebanese media on Tuesday reported that an FBI report was given to a Lebanese judge on Monday. The FBI declined to comment on the reports. Two US government sources said that US agencies were also largely convinced that the blast, involving large quantities of ammonium nitrate which had been stored in a port building for years, was an accident. A European government source said European experts also assessed that the explosion was accidental.