Authorities in Washington, D.C. are investigating three more suspicious letters containing white powder that may have been sent from the Dallas area.
WRC-TV, NBC 4 in D.C., says police and fire officials are investigating letters sent to a restaurant and elementary school in the area. A third letter was also found on Thursday.
Federal law enforcement released a bulletin about the recent mailings:
A series of “white powder letters” were received in the District of Columbia in October, 2010 and May, 2011. Similar letters were received at various locations around the country March 6, 2012 and additional letters may be in the mail system pending delivery. Specially trained response teams are prepared to investigate and collect any suspicious letters.
The letters are postmarked Dallas,Texas and contain a letter with the words AL AQEDA-FBI or similar language and contain a white powder. They are typically addressed using a computer printed label.
There have been seven letters received in D.C. this week. Closer to home, six similar letters were received in North Texas this week, including many sent to local elementary schools.
Additionally, letters containing a seemly harmless white powder were sent to a gallery in New York City, a bank building in Birmingham, Ala., and a middle school in Connecticut, in addition to the previously mentioned letters sent to Washington, D.C
The FBI has declined to discuss whether all the letters are connected, however NBC investigations have revealed some letters and packages contained postmarks from Grapevine and Dallas, TX
The U.S. Postal Inspection Service said several safety measures are in place and customer should feel comfortable that their mail is secure.
All of the mail that goes through North Texas' processing facilities go through a bio-hazard detection machine that scans the envelope for dangerous substances.
NBC 5 learned Monday that a letter sent to a gallery in Manhattan was postmarked in Grapevine.
"If a letter is actually postmarked Grapevine, that would mean it would have to come across the counter," said Amanda McMurrey, of USPIS.
Powdery substances found on mail have been a concern since a series of anthrax-laced letters were mailed around the United States in the wake of the Sept. 11, 2001, terrorist attacks. Since that time, a number of hoaxes have been perpetrated.
The current crop of letters may be linked to hundreds of unsolved hoaxes since 2008.