An FBI team has started its investigation into a deadly bombing of a U.S. convoy (searchafter the arrest of seven militants from a rogue Palestinian group.

Separately, Israeli Prime Minister Ariel Sharon (searchappeared to rule out the threat of expelling Palestinian leader Yasser Arafat (search), telling an Israeli daily that such a move would be bad for Israel.

"Our calculations have been for years that expelling him would not be good for Israel," Sharon said in an interview published Friday in the Jerusalem Post.

Late Thursday, the bodies of the three Americans killed in Wednesday's bombing -- John Branchizio, 36; Mark T. Parson, 31; and John Martin Linde Jr., 30 -- were brought to Israel's international airport outside Tel Aviv, for a short memorial ceremony and flown home.

"They were a credit to their country and to our community. We are proud of them, and we mourn their loss," U.S. Ambassador Dan Kurtzer said eulogizing the three security guards. Afterward, the coffins, draped with American flags, were put aboard a plane.

U.S. Embassy spokesman Paul Patin said the FBI team had started an "open-ended" investigation into the attack that also wounded an American guard. Patin said he did not have details of the probe, but thought "it might involve going to the attack site."

The Americans died on the main north-south highway in Gaza when assailants detonated a remote-controlled bomb with dozens of pounds of explosives. After the attack, American investigators were forced to flee the scene by Palestinian stone throwers.

Palestinian police were greeted Thursday by gunfire when they arrived and searched seven homes in the Jabliya refugee camp to make the arrests. Later in the day, officers tried to detain another suspect in Jebaliya, but aborted the mission when they came under machine-gun fire.

The seven suspects are members of the Popular Resistance Committees, a group of dozens of armed men from various factions, many of them former members of the security forces and disgruntled followers of Yasser Arafat's Fatah movement.

A Palestinian source said none of the suspects themselves had served in the security forces Arafat controls, but the group's links to the security forces could prove embarrassing to Arafat.

The Popular Resistance Committees were formed at the end of 2000, three months after the outbreak of Israeli-Palestinian fighting. They consist mainly of Fatah breakaways and ex-security men. Other factions, including Hamas and Islamic Jihad, are also represented.

The group believes the use of force is the only way to end Israeli occupation of the West Bank and Gaza Strip. Israeli officials said the group has ties to the Lebanese guerrilla group Hezbollah.

The Palestinian group has blown up three Israeli tanks with massive remote-controlled bombs in the past two years -- the same technique used in Wednesday's attack.

No Palestinian group has claimed responsibility for the bombing, the first deadly attack targeting Americans in the Palestinian areas.

Arafat security adviser Jibril Rajoub promised a thorough investigation.

"I am 100 percent sure that we will be able in the coming days to reach who planned and carried out this attack," he told Israel Radio.

In an apparent nod to the United States, Arafat placed all nine Palestinian security units in the Gaza Strip under a single commander, Maj. Gen. Abdel Razek Majaidie. The United States has demanded reforms in the Palestinian Authority -- especially in the security forces -- and a crackdown on militant groups.

The attack could lead to a further U.S. disengagement from mediating the conflict and could deter the international community from sending large numbers of monitors -- a long-standing Palestinian request.

Sharon's comments on Arafat backtracked on a Sept. 11 Israeli Cabinet decision that decided "in principle" to get rid of the Palestinian leader. The decision came two days after a pair of Palestinian homicide attacks that killed 15 Israelis.

Both Israel and the United States have attempted to sideline Arafat, calling him an "obstacle to peace," and have tried to encourage the emergence of an alternative Palestinian leadership.

Sharon said that Israel was reluctant to try to expel Arafat because "the likelihood of expelling him without harming him is low."

Israeli forces on Thursday continued a large-scale operation in the Rafah refugee camp on the Gaza-Egypt border, searching for tunnels allegedly used by Palestinians to smuggle weapons from Egypt.

A member of the Palestinian security forces and a man identified by local people as a gunman were killed, and 13 people were wounded in sporadic exchanges of fire, hospital officials said.

Israel also announced the arrest of a member of the Palestinian Coast Guard who allegedly smuggled weapons into Gaza from Egypt.

In a separate development, Israel said Friday that it had lifted three roadblocks in the Gaza Strip, letting Palestinians move freely through most of the area. The roadblocks, erected on Oct. 5 after a homicide bombing in the Israeli city of Haifa, were removed late Thursday after a "security assessment," a military source said, declining to elaborate.