BEIRUT >> A team of FBI investigators was due to arrive in Lebanon this weekend to take part in the probe of Beirut’s massive explosion, a senior U.S official said today after visiting the location of the blast.

David Hale, U.S. undersecretary of state for political affairs, called for a thorough and transparent investigation. He said the FBI team is taking part at the invitation of Lebanese authorities to find answers about what caused the Aug. 4 explosion that killed nearly 180 people and wounded thousands.

The cause of the fire that ignited nearly 3,000 tons of ammonium nitrate at Beirut’s port remains unclear. Documents have emerged showing the country’s top leadership and security officials were aware of the chemicals stored at the port. French investigators are also taking part in the Lebanese-led probe.

“We really need to make sure that there is a thorough, a transparent and credible investigation. I know that is what everyone is demanding,” Hale said.

Search and rescue crews flew in from around the world in the immediate aftermath. Hale toured the site of the blast with Lebanese army officers.

Many Lebanese want the probe taken out of the hands of their government, fearing that bickering among the long-entrenched political factions, notorious for corruption, won’t allow any results to come to light that are damaging to their leadership.

Top Lebanese officials, including President Michel Aoun, have rejected calls for an independent probe, describing it as “a waste of time” that would be politicized.

Late on Friday, the leader of the powerful Hezbollah group said he did not trust any international investigation, a clear reference to the FBI assistance. Hassan Nasrallah said the cause of the explosion is still unclear, adding that any international probe would likely seek to clear Israel of any responsibility in the port explosion, if it had any.

Nasrallah added that Israel will be met “with an equally devastating response” if the investigation points to its involvement.

Israel has denied involvement and so far no evidence has emerged suggesting otherwise. However, Aoun, who is supported by Hezbollah, has said it’s one of the theories being investigated.

On Saturday, French investigators were seen in boats and on the ground near the scene of the blast. A French helicopter carrier was docked at the port as French troops unloaded equipment.

French troops on foot and in vehicles were moving around the port. At a commercial part of the port undamaged by the blast, workers unloaded wheat. The U.N says 30% of the port remains operational.

Hale, the U.S. official, stressed the need for full state control over ports and borders in an apparent reference to claims that Hezbollah holds influence over both in Lebanon. “We can never go back to an era in which anything goes at the port or borders of Lebanon,” he said.

The U.S. and its allies consider Hezbollah a terrorist organization, and have accused the Iran-backed group of abusing government funds. Local media have speculated that Hale would be pushing for a government that excludes Hezbollah.

Under pressure, Lebanon’s government resigned Aug. 10. For now, there are no formal consultations underway on who will replace Hassan Diab as prime minister and no likely candidate has emerged. But the flurry of diplomatic visits appeared designed to influence the forming of the new government.

Popular anger has swelled over the ruling elite’s corruption, mismanagement and political uncertainty. Western leaders have said they will send aid directly to the Lebanese people and that billions of dollars will not be pumped into the country before major reforms take place.

On Friday, the United Nations launched a $565 million appeal for Lebanon with immediate humanitarian assistance and initial recovery efforts. Last week, international donors pledged nearly $300 million of emergency assistance to Lebanon.

Najat Rochdi, U.N. humanitarian coordinator for Lebanon, called for more funds to cover the critical needs of shelter, food, health and education.

“We hope that the emergency response doesn’t last for too long because the best thing to do is for people to go back to their normal life, for people to start healing,” she said.

Rochdi said most donors have asked that aid be channeled through the U.N., which she said would be coordinated with Lebanon’s armed forces to ensure access.

“We will be very strict about the use of humanitarian assistance. We will be monitoring closely every single delivery of our humanitarian assistance,” she said. “We will be accountable not only to donors because our accountability goes also to the affected population.”

Also on Saturday, families and friends buried Ralph Malahi, a 23-year old firefighter who was among 10 firefighters killed in the explosion.

Malahi was given a hero’s funeral in Beirut in which the procession started from the firefighter center. Lifting Malahi’s coffin, thousands paraded through different parts of the city, firing weapons in in the air in commemoration. His body finally arrived at a church in the Furn el-Chebak neighborhood where prayers were held for Malahi.

Malahi is the seventh firefighter to be retrieved from under the debris in the port at the scene of the blast. Three remain missing.

Malahi’s mother, weeping, blamed the government for her son’s death. “Why did you not evacuate the port?” she said, in reference to the government’s knowledge that highly explosive material was stored at the port.