DALLAS - More than 20 letters that contained a white, powdery substance delivered to District of Columbia schools on Thursday are similar to those mailed to schools elsewhere in the U.S. over the last several weeks, the FBI said.
The letters were mailed from a North Texas post office, so now the Dallas-Fort Worth office of the U.S. Postal inspection Service is part of the investigation.
"At this point, they are still at the lab for testing," said Amanda McMurrey, U.S. Postal Service Inspection. "So, the presumptive has been negative. They are screened on sight. At this point, there is no sign of any hazardous material, but to followup that presumptive test it will go to the lab and that will take up to three days."
The letters included the words "FBI," "al-Qaida" and "U.S.A.," which makes them similar to letters mailed in 2008 to Gov. Rick Perry and several other governors. Those case remain unsolved. It is too early to say if those letters share the same source that led to alarm Thursday. Mailing such letters is a felony offense and there is a major reward for anyone who can help solve the case.
"This is generally considered an act of terrorism or hoax terrorism," McMurrey said. "There are a variety of charges the United States attorney could bring, and they bring five to ten years per charge."
Law enforcement sources told ABC7 News that all the letters appear to contain the same contents. One of the officials said it had the look and consistency of cornstarch. No one was injured by the powder. Authorities don't know if the packages came from the same sender.
The envelope at the School Without Walls contained white powder in a folded sheet of paper. It stated "al quaida, fbi, usa" and was from North Dallas, Texas.
WFAA"s Gary Reaves and The Associated Press contributed to this report