Al Qaeda may be planning attacks

Level of 'chatter' high, officials say

A U.S. Park Ranger stands guard outside Philadelphia's Independence Hall on Monday.

WASHINGTON (CNN) -- Intelligence gathered in recent weeks has raised serious concerns that terrorists may try to strike against the United States again this summer, according to U.S. officials.

Although there are no specific indications about what targets al Qaeda may hope to attack, there are "a lot of indications that something is up," one U.S. intelligence official said.

The level of "chatter" by individuals suspected of association with al Qaeda and related terrorist groups has been high, officials said, as it was last summer prior to the September 11 attacks on the World Trade Center and the Pentagon.

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One difference now is that the United States and international news media are broadcasting reports about security preparations for July Fourth festivities, which might have a tendency to create "a self-fulfilling prophecy" in raising the apparent threat level, one official said.

He said "bad actors" have seen the warnings and can be overheard talking among themselves about whether an attack is coming during the week of the nation's birthday.

U.S. officials said they have no evidence an attack is planned this week.

Meanwhile, officials expressed skepticism about a Time magazine report that quoted French intelligence officials as saying a handwritten note from al Qaeda leader Osama bin Laden was found in the house where Abu Zubaydah, the terrorist network's operations chief, was captured.

"Not to the best of my knowledge," said a senior intelligence official. The official did say, however, that documents were found in the house in Pakistan indicating that bin Laden and his top lieutenant, Ayman al-Zawahiri, were still alive as of December.

Officials are also skeptical about a report suggesting bin Laden may have secondary osteoporosis, a condition that can produce crippling back pain.

"We think that is wrong," said one official. In the past, U.S. officials have also said they doubt bin Laden has ever required kidney dialysis, as some reports indicated, although they said he may have suffered from kidney stones at one point.

Threat level remains at yellow

Earlier Monday, Bush administration officials said they have no plans to revise the homeland security alert status for the July Fourth holiday, although extra security precautions are being taken and law enforcement officials have been asked to be on alert.

Senior administration officials, including Homeland Security Director Tom Ridge and Attorney General John Ashcroft, met Monday at the White House to discuss the latest information on terrorist threats. They agreed the nation is on "yellow," or "elevated," status.

A snow fence security perimeter encloses portions of the Mall around th Washington Monument in preparation for the nation's July 4 celebration.

According to the five-step color-coded threat assessment used by the White House Office of Homeland Security, yellow is the mid-point color, meaning the government considers the nation to be at a "significant risk of terrorist attacks."

"Orange," or "high," is the next level -- meaning the government considers there to be a "high risk of terrorist attack." "Red," or "severe," is the highest alert status, and means just what its name implies.

The government has sent general advisories to law enforcement agencies across the country urging them to be extra vigilant around the holiday, and security precautions are being taken at key government and other installations in the Washington area, officials said.

A Secret Service source, for example, said additional steps are being taken around the White House and for other officials and installations under its protection, "but nothing that should be visible to the eye and nothing that is in response to anything other than a sense of caution."

Several administration officials said there is no specific, credible information about threats on the United States to warrant raising the alert status from the yellow level.

-- CNN correspondents David Ensor and John King contributed to this report.