By SAM F. GHATTAS, Associated Press Writer,  BEIRUT, Lebanon – FBI agents on Wednesday joined the investigation into the latest of a spate of explosions in Lebanon
A U.S. Embassy official declined to discuss the matter Wednesday, other than to say that "the U.S. is happy to respond positively to requests from the government of Lebanon." The official did not wish to be named, but U.S. Ambassador Jeffrey Feltman said Tuesday the U.S. team was to assist the Lebanese in the investigation and provide technical expertise.

Syria, which was forced to withdraw its army from Lebanon in April, has come under intense pressure from the United States. Washington has warned Damascus to stop interfering in Lebanese affairs. Syrian officials also are the target of the U.N. probe into Hariri’s assassination.

The chief U.N. investigator, German prosecutor Detlev Mehlis, met with Prime Minister Fuad Saniora. Details of their discussions were not disclosed, but Mehlis met late Tuesday with Justice Minister Charles Rizk.

"What Mr. Mehlis told me is of such importance," Rizk told reporters Wednesday, that he had asked Saniora to meet with the German investigator. He did not elaborate.

U.N. investigators returned to Lebanon on Friday after four days of questioning officials in Syria, whose army and intelligence units were in control of Lebanon when a massive bombing targeted Hariri’s motorcade on a Beirut street, killing him and 20 others.

Mehlis is expected to issue his report in late October.

The Hariri probe could possibly implicate Syria and some of its allies in Lebanon. Already four Lebanese security generals close to Syria are under arrest on suspicion of involvement.

The possibility of the probe’s findings reaching President Bashar Assad’s regime in Syria has given rise to public fears of increased violence in Lebanon, where Saniora linked the spate of bombings to the U.N. probe and predicted there could be more attacks.

Interior Minister Hassan Sabei has publicly warned of a "terrorist plot" to destabilize Lebanon and suggested the government was helpless to prevent more attacks.

The attempt to kill Chidiac, who lost an arm and a leg in the explosion, provoked wide indignation in Lebanon. The United States, the European Union and the United Nations joined Lebanese politicians in condemning the bombing, while students staged protests in Beirut.

Anti-Syrian groups have blamed Syria for Hariri’s assassination and the recent bombings. Damascus has denied involvement.