WASHINGTON — U.S. intelligence agencies have found no evidence that al-Qaida has sneaked any terrorists into the country for a strike coinciding with the 10th anniversary of the Sept. 11 attacks, the Associated Press reported Saturday, citing unnamed senior officials.
But authorities kept a high alert as investigators looked for proof of a plot possibly timed to disrupt events planned today in Washington or New York.
Since late Wednesday, counterterrorism officials have chased a tip that al-Qaida may have sent three men to the United States on a mission to detonate a car bomb in either city. At least two of those men could be U.S. citizens, according to the tip.
No intelligence supported that tip as of Saturday, and officials continued to question the validity of the initial information.
While such tips are common among intelligence agencies, this one received more attention, and government officials chose to speak publicly about it, because of the connection to the anniversary of the worst terrorist attack in U.S. history.
Al-Qaida long has hoped to strike again on the anniversary.
At the FBI field office in Washington, assistant director James McJunkin described the tip and the response as routine. The United States already had bolstered security nationwide before the forthcoming anniversary and anticipated an increase in tips.
"We expect we're going to get an increase in threats and investigative activity around high-profile dates and events," McJunkin said. "This is a routine response for us."
Intelligence analysts have looked at travel patterns and behaviors of people who recently entered the country. While they have singled out a few people for additional scrutiny, none has shown any involvement in a plot, the Associated Press reported, citing unnamed senior U.S. officials who insisted on anonymity because they were discussing intelligence.
President Barack Obama met with his national security team Saturday, but the White House released no new information about possible threats. A statement said that counterterrorism efforts were working well and would not ease in the weeks and months ahead.
The tip that touched off the most recent investigation came from a CIA informant who has proved reliable in the past, the Associated Press reported, citing unnamed U.S. officials. The informant reportedly approached intelligence officials overseas to say that the men were ordered by new al-Qaida leader Ayman al-Zawahri to mark the 10th anniversary of the Sept. 11 by doing harm on U.S. soil.
Zawahri took over as the group's leader after the United States killed Osama bin Laden during a raid in May at his compound in Pakistan.
Counterterrorism officials were looking for certain names associated with the threat, but it was unclear whether the names were real or fake. The informant said the would-be attackers were of Arab descent and might speak Arabic as well as English.
Some intelligence officials raised doubts about the threat, given the short turnaround time. Someone who recently arrived in the United States would have just days to plan and obtain materials for a car bomb attack, a difficult feat even with a long lead time.
But the threat was not dismissed. Extra security was put in place to protect the people in the two cities that took the brunt of the jetliner attacks that killed nearly 3,000 people at the World Trade Center and the Pentagon.
Police in New York were investigating two vans stolen from a World Trade Center site contractor and another from a New Jersey storage facility. Police in Washington were on the lookout for a pair of U-Haul vans reported missing from nearby Prince George's County, Md., though U-Haul said one was later found.