Based upon detailed intelligence that showed al Qaeda plots to blow up specific buildings with car bombs, the federal government has learned that terrorists studied every aspect of those buildings in the financial services sectors of New York, Washington and Newark, N.J., including the thickness of window glass.

Based on the information the federal government raised the terror alert level yesterday to orange. The potential targets are the International Monetary Fund and World Bank Headquarters in Washington; the New York Stock Exchange and Citigroup Center in New York; and the Prudential Financial Building in Newark.

According to an article in today's Washington Post, the intelligence "shows that al Qaeda has been methodically casing those buildings, and perhaps others, since well before the September 11, 2001, attacks on the Pentagon and World Trade Center …"

The article reported that the surveillance included details ranging from the location of security desks and cameras in the buildings to "what kinds of explosives would do the most damage to the structures." The article went on to state, "the operatives focused on structural features of the targets that might 'prevent the buildings from toppling down,' including the thickness of window glass."