Federal law-enforcement officials said that among the intelligence picked up recently were two electronic transmissions that discussed the possibility of an attack on New York, Washington, Boston and more broadly the U.S. coastlines
Overseas, U.S. officials also took additional security measures. The United States, Britain and Germany temporarily closed their embassies and consulates in Saudi Arabia on Tuesday following warnings.
The Federal Aviation Administration is planning to temporarily prohibit flights over sports stadiums and restrict small private planes flying within a 17.25-mile radius of the Washington Monument, said agency spokeswoman Laura Brown.