Homeland Security Secretary Michael Chertoff announced a targeted raise in the threat level.
"The thoughts and prayers of the American people are with the victims of this tragedy and our friends in Britain."
In light of [Thursday's] attacks in London, the United States government is raising the threat level from Code Yellow – or Elevated – to Code Orange – or High – targeted only to the mass transit portion of the transportation sector.
This only includes regional and inter-city passenger rail, subways and metropolitan bus systems. We are also asking for increased vigilance in other transportation systems.
Currently, the United States has no specific, credible information suggesting an imminent attack in the United States. However, we know the tactics and methods of terrorists, as demonstrated by the horrific rail bombings in Madrid last year.
The intent of al Qaeda and affiliated organizations to attack in Europe and the United States has been well documented and continues to be reflected in intelligence reporting."