Authorities believe the terror threat about a possible Al Qaida plot to attack New York or Washington, D.C. this weekend could involve a dirty bomb, CBS New York reported.
According to reports, the alleged plot involves detonating car bombs on bridges and in tunnels in New York and D.C. to coincide with the tenth anniversary anniversary of 9/11.
Sources told CBS intelligence suggests the threat could be a dirty bomb, with terrorists mixing radiological isotopes with an explosive device.
"We have to think about a dirty bomb, where you take radiological material and mix it with conventional explosives," New York City Police Commissioner Raymond Kelly said.
In response, the NYPD is deploying radiation detectors, including panel trucks with sophisticated instruments. On Friday, police officers had personal radiation detectors on their belts, and detectors are being used within a 50-mile radius of New York City — in New Jersey, Connecticut, and Pennsylvania and on Long Island.
Three suspects are currently being sought, at least two of whom authorities believe could be U.S. citizens. They are believed to be of Pakistani origin and possibly fluent in English.
There is also enhanced concern that Times Square could be the target, to finish the job of Faisal Shahzad's failed car bomb attempt in May 2010.
Security officials told CBS this is how Al Qaida operates: After their 1993 attempt on the World Trade Center did not succeed in causing widespread carnage, they struck again on Sept. 11, 2001.
According to CBS, some of the information on the latest threat could be coming from senior Al Qaida operative Younis al-Mauritani, the man hand-picked by Osama bin Laden to develop terror targets in the United States.
Al-Mauritani was arrested in Pakistan last week with his computer, BlackBerry and other tools.