WASHINGTON — Officials searched for suspicious packages in the United States and other countries after two shipments containing explosives, sent from Yemen and addressed to synagogues in Chicago, were intercepted in Britain and Dubai.

The discovery of the explosives packed in toner cartridges for computer printers, based on a tip from Saudi intelligence officials, set off a broad terrorism scare on Friday that included the scrambling of fighter jets to accompany a passenger flight as it landed safely in New York.

Cargo planes were moved to secure areas of airports in Philadelphia and Newark for searches, and a United Parcel Service truck in Brooklyn was stopped and inspected. No additional explosives had been discovered by early Saturday morning.

Representative Jane Harman, a California Democrat on the House Homeland Security Committee, said Friday that the packages seized in Britain and Dubai contained PETN, the same chemical explosive contained in the bomb sewn into the underwear of the Nigerian man who tried to blow up an airliner over Detroit last Dec. 25. That plot, too, was hatched in Yemen, a country that is regarded as one of the most significant fronts in the battle with extremists.