U.S. intelligence officials warned last month that terrorists want to mail chemical and biological materials as part of an attack against the country.
The Sept. 23 bulletin from the Homeland Security Department, obtained by The Associated Press, says the government has credible information that terrorists were interested in carrying out an attack on the U.S. and other Western countries using the mail.
The U.S. had issued similar warnings in the past.
Thursday night, authorities intercepted an explosive device in Dubai and another suspicious package in England. Both were mailed from the same address in Yemen, bound for Chicago Jewish organizations. The White House has called this a potential terrorist threat.