RIYADH, Saudi Arabia - Secretary of State Colin Powell toured the twisted wreckage left by a terrorist bombing Tuesday, and President Bush promised those responsible for killing Americans "will be brought to justice."
The administration ordered most U.S. diplomatic personnel home from Saudi Arabia.
While nonessential diplomats and family members were directed to leave the country, FBI investigators were sent in, their mission to help with the probe of what Saudi officials said was the deadly work of al-Qaida.
In Riyadh, the smell of explosives hung in the air and a U.S. flag dangled from the roof of one destroyed building as Powell described the bombing as "criminality, terrorism at its worst."
Half a world away, Bush said those responsible would be tracked down. "It doesn't matter how long it takes, the war on terror goes on," he said after visiting parts of Missouri damaged by tornados.
Bush also said he "wouldn't be surprised" if al-Qaida, which carried out terrorist attacks in the United states on Sept. 11, 2001, was behind the Saudi attacks.
State Department officials said Tuesday evening that eight Americans died in the attack, and 17 remained hospitalized.
With the investigation scarcely under way, Powell told reporters that "the facility had been cased" before an attack that he called "very well executed."
U.S. officials said Saudi guards posted at the entrance to the complex were shot to death. And one senior administration official, speaking on condition of anonymity, told reporters on Powell's plane that it took the bombers "30 seconds to a minute" to get through the gate guarding a housing complex for employees of the Virginia-based Vinnell Co., drive the truck to the building, and detonate their explosives.
"They had to know where the switches were," this official said, suggesting the bombers had inside information.
The State Department's travel warning said all nonessential diplomatic personnel and family members from the official American community were ordered to depart. The directive applies to Americans from the U.S. Embassy and from consulates in Saudi Arabia.
Echoing a travel warning issued 12 days earlier, the statement recommended that private U.S. citizens currently in Saudi Arabia consider departing the country and that Americans defer nonessential travel there.
"U.S. citizens are reminded of increased security concerns and the potential of further terrorist attacks in Saudi Arabia," it said.
Vinnell, a subsidiary of Northrop Grumman Corp., has a contract to train Saudi Arabian National Guardsmen. Seventy Americans employed by the company lived in the building, but 50 of them were away on a training exercise at the time of the attack.
In a statement, Northrop Grumman said nine of its employees were killed, including seven Americans. Details on the death of the eighth American were not immediately available. Other employees remained hospitalized after the attack, two in serious condition.
The complex was one of three hit by synchronized suicide bombings Monday night that left at least 20 dead. Authorities found nine other bodies believed to be those of the attackers, a Saudi Interior Ministry official said.
The State Department announced May 1 that terrorist groups might be in the final phases of planning attacks against U.S. interests in Saudi Arabia. The bombings occurred at a time when U.S. officials had said al-Qaida - blamed for the attacks of Sept. 11, 2001 - had been significantly weakened by a 20-month campaign that included U.S.-led wars in Afghanistan and Iraq.
Osama bin Laden, the head of al-Qaida, is a native of Saudi Arabia. He has long been opposed to the presence of American troops - whom he refers to as "infidels" - in his homeland.
While Bush pledged to find and punish those behind the attacks, one Democratic presidential hopeful renewed his claim that the administration should have focused its energy on al-Qaida over the past year rather than prepare and launch a war against Iraq.
"The war on Iraq was a distraction," Sen. Bob Graham, D-Fla., told reporters at the Capitol. "It took us off the track of the war on terror which we were on a path to win, but we've now let it slip away from us."
Elsewhere in Washington, counterterrorism officials said they were investigating whether any of the bombers came from a group of suspects who escaped Saudi authorities last week.
Investigators also are trying to determine who oversaw the operation, and inquiring whether senior al-Qaida operatives, believed to be in Iran, played a role, according to Bush administration officials who spoke on condition of anonymity.
Several top al-Qaida operatives are believed to be in Iran, with at least the tacit consent of some elements of the Iranian government, U.S. officials have said. Bin Laden's son, Saad, is thought to be among them.
Bush said "I have no idea" whether Iran was involved.
Asked about al-Qaida, he said, "I can't say for certain it was al-Qaida yet, but I wouldn't be surprised if it was."
Other members of his administration, Powell and FBI Director Robert Mueller among them, as well as several lawmakers, said the signs pointed toward an attack carried out by al-Qaida.
Powell was in Amman, Jordan, at the time of the attack, making the rounds of Middle Eastern countries in hopes of producing momentum toward Middle East peace.
He flew to Saudi Arabia as planned, and altered his schedule to visit the site of the bombing that killed Americans. "This was a well-planned terrorist attack, obviously," he said.
The FBI "assessment team" will include up to a dozen agents, bomb specialists and technicians, bureau spokesman Bill Carter said.
FBI investigators will be depending on cooperation from the Saudis, who restricted agents' access to witnesses and suspects after the 1996 bombing of the Khobar Towers dormitory that killed 19 U.S. military personnel.
Saudi officials have been eager to blunt U.S. criticism since the Sept. 11 attacks that they have allowed al-Qaida operatives to operate within the country. More than 300 suspected terrorists have been arrested in Saudi Arabia since the attacks, Saudi officials say.
"My expectation is that we will get full cooperation from the Saudis," Mueller said in an appearance in Albany, N.Y.
It was the second time in eight years that the Saudi business interests of Vinnell Corp. have come under terrorist attack.
A November 1995 car bomb destroyed a building in the Saudi capital that was headquarters for a U.S. Army training program in which Vinnell was deeply involved.
The Saudi National Guard protects the ruling monarchy and is the Saudi equivalent to the Republican Guard of Saddam Hussein, said John Pike, director of Globalsecurity.org, a defense policy group. The National Guard is distinct from the regular Saudi Army.