MOSCOW, April 6 (JTA) — A powerful blast outside a downtown Moscow office of Russia’s Federal Security Service on Sunday may have been the work of the same people who bombed a Moscow synagogue last May. Sources in the Federal Security Service, the successor to the Soviet-era KGB, said the bomb that injured three people and shattered dozens of windows was identical to the device used in the bombing of the Marina Roscha Synagogue. Security service officials also said that both had been planted in a similar manner. The officials gave no explanation why those responsible for the synagogue attack would want to bomb the Federal Security Service office. Security officials have made little progress in their investigation of the synagogue bombing, which caused no injuries but seriously damaged the building. Sunday’s bombing did not affect the main headquarters of the Federal Security Service, the once much-feared KGB complex on Lubyanka Street, located several hundred feet away from the blast site. Other officials with the Federal Security Service believe that Sunday’s bombing may have been the work of the same obscure group that claimed responsibility for a failed grenade launcher attack on the U.S. Embassy in Moscow late last month. That attack was reportedly carried out to protest the U.S.-led NATO military operation in Yugoslavia. The group that claimed responsibility for the failed embassy attack recently urged those U.S. citizens who were not in favor of the NATO air strikes to leave Moscow by last Saturday. The group, called Skif — which means Scythian, an ancient warlike people — said it would continue “acts of retribution” against those Americans remaining in Moscow after its deadline.