Suspicious Packages Found On Flights In Philadelphia, Newark WASHINGTON Authorities in Dubai intercepted an explosive device bound for a Chicago-area Jewish institution aboard a cargo jet, officials disclosed Friday, triggering a worldwide alert and fears that al-Qaida was attempting to carry out fresh terror attacks. A second package like the first, shipped from Yemen was discovered aboard a plane in England. It, too, was addressed to a Jewish organization in the Chicago area, although there was no immediate confirmation about its contents. Several other cargo planes at airports along the Eastern Seaboard of the United States also were searched, and officials said no explosives were found. An Emirates Airlines passenger jet carrying cargo from Yemen was escorted from the Canadian border to New York City by two military fighter jets, U.S. officials said. They said it was a precautionary action. President Barack Obama arranged to make a statement about the developments at the White House. Aides said he had been informed about a "potential terrorist threat." "The president directed U.S. intelligence and law enforcement agencies and the Department of Homeland Security to take steps to ensure the safety and security of the American people, and to determine whether these threats are a part of any additional terrorist plotting," the White House said in a statement. An FBI spokesman in Chicago, Ross Rice, said both suspicious packages had been sent from the same address in Yemen. U.S. officials said they were increasingly confident that the packages were part of a plot by Yemen's al-Qaida branch, the same group responsible for an attempted bombing of a U.S.-bound airliner last Christmas. They spoke on condition of anonymity, citing the ongoing investigation. Other officials, also speaking on condition of anonymity, said the package found in England contained a printer toner cartridge with wires and powder. It was discovered aboard a plane in East Midlands, north of London. One official said intelligence personnel had been monitoring a suspected plot for days. The packages in England and Dubai were discovered late Thursday after a foreign intelligence service picked up information related to Yemen and passed it on to the U.S., this official said. Confirmation that the package discovered in Dubai contained explosives came from an official United Arab Emirates security source who likewise spoke only on condition of anonymity. U.S. intelligence officials warned last month that terrorists hoped to mail chemical and biological materials as part of an attack on America and other Western countries using the mail. The alert came in a Sept. 23 bulletin from the Department of Homeland Security and obtained by The Associated Press. In the hours following the discoveries, Yemeni officials said they had launched a terrorism investigation, and Scotland Yard said its investigators were testing a number of additional items seized from the plane in East Midlands. U.S. authorities conducted searches of aircraft in Philadelphia, Newark, N.J., and New York City. Local officials said all of the suspicious items and planes that were searched had been given the "all clear." That was before the plane escorted by fighter jets landed in New York. "As a precaution, DHS has taken a number of steps to enhance security," the Homeland Security Department said in a statement. "Some of these security measures will be visible while others will not." One was spectacularly so. Two U.S. fighter jets were dispatched to escort the Emirates Airlines flight, which landed at New York's John F. Kennedy International Airport without incident. Since the failed Christmas bombing of a Detroit-bound airliner, Yemen has been a focus for U.S. counterterrorism officials. Before that attack, the U.S. regarded al-Qaida's branch in Yemen as primarily a threat in the region, not to the United States. The Yemen branch known as al-Qaida in the Arabian Peninsula has since become a leading source of terrorist propaganda and recruiting. Authorities believe about 300 al-Qaida members or cells operate in Yemen. The Yemeni government has stepped up counterterrorism operations, with help from the U.S. military and intelligence officials. Mohammed Shayba, general-director of the state airline's cargo department, said the government is conducting an investigation. "Those in charge are in constant meetings and they are investigating and taking the issue seriously," he told The Associated Press. ___ Associated Press writers Adam Schreck in Dubai, Maryclaire Dale, Randy Pennell and Jonathan Poet in Philadelphia, Joshua Freed in Minneapolis, Colleen Long in New York, Shawn Marsh in Trenton, N.J., Ahmed al-Haj in San'a, Yemen, Carla K. Johnson in Chicago, Lolita Baldor in Washington, and Sylvia Hui, Jill Lawless, Paisley Dodds, Greg Katzand and Raphael Satter in London contributed to this report.