The hunt continued on Friday for three men – one a U.S. citizen – believed to be planning a massive car-bomb attack to mark Sunday’s tenth anniversary of 9/11.
But information on the nature of the threat, aimed at bridges and tunnels in either Washington or New York City, is so vague that agents from the FBI and the Department of Homeland Security have a huge job on their hands.
Security was stepped up in the two cities and at major transportation hubs around the country, with police in the nation’s capital being told they will all be working 12-hour days for the foreseeable future.
"We do have talk about using a car bomb. We've been told that was an intention...It was from a credible source," Vice President Joe Biden said on ABC’s "Good Morning America."
But he added, “There is no certitude. We don’t have a smoking gun.”
First word of the plot came on Wednesday night. President Barack Obama and key advisers were briefed early Thursday, but news only became public later in the day, shortly before Obama’s jobs speech to a joint session of Congress.
It was treated with such seriousness that New York Mayor Michael Bloomberg appeared on television for a 10 p.m. news conference, interrupting NBC’s coverage of the NFL season opening game between the Green Bay Packers and the New Orleans Saints.
"We know the terrorists regard the anniversary as an opportunity to strike again. We do live in a world where we must take these threats seriously," Bloomberg said.
“The NYPD is deploying additional resources around the city and taking additional steps to keep our city safe, some of which you may notice and some of which you will not notice," Bloomberg said. "But there's no reason for any of the rest of us to change anything in our daily routine."
Reports say that the hunt is centered on three people who have recently entered the United States. They are believed to have started their journey from the tribal areas of Pakistan and may have traveled through Dubai.
Authorities say the attack was “to avenge Osama bin Laden’s death,” but say they have not yet identified suspects. Now they are trawling through lists of people who have come to the United States over the past four weeks.
Biden pointed out that documents found in bin Laden’s lair in Abbottabad, Pakistan, suggested he had been plotting a terror attack on the U.S. to coincide with the 9/11 anniversary.
The “very specific” information comes from a source, believed to be based in Pakistan, who has proved reliable in the past, but the FBI has been unable to find confirmation from a second source.
"Credible means this is something they've been expecting, something that could happen," former White House counter-terrorism advisor Richard Clarke said. "Unconfirmed means they have one source... Sometimes people make up stories and pass them on to the CIA in great detail."
Sources have said that one of the three men is a U.S. citizen and the other two have paperwork, either Green Cards or visas, which allow them to visit the country legally.
ABC said officials had told them that the plan had been initiated by Ayman al-Zawahiri, the man who succeeded bin Laden as head of al-Qaida.
The New York Post reported that the attack was planned for Saturday, Sunday or Monday.
Obama is due to be in both Washington and New York on Sunday, the day of the anniversary. He will be at the memorial at Ground Zero in the morning and then give a speech during a concert at the Kennedy Center in the evening.
The heightened security was apparent in New York on Friday morning with authorities stopping traffic on the 59th Street Bridge between Manhattan and Queens, causing major back-ups. The Brooklyn Bridge was down to one lane.
Checkpoints were set up in Times Square and elsewhere in midtown.
Armed police and National Guards in bulletproof vests were on duty at Grand Central Terminal and Penn Station and officials swabbed passengers’ bags looking for explosives.
Police presence was also increased at Kennedy, La Guardia and Newark airports and at bridges and tunnels throughout the city.
In Washington, police chief Cathy Lanier said the public should expect more stopped vehicles, with officers passing out fliers urging the public to alert authorities about abandoned or suspicious vehicles or people who are loitering.
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