Five letters containing harmless white powder received in North Texas appear similar to several other scares across the country on Monday and also could be linked to hundreds of unsolved hoaxes since 2008.
The FBI confirmed agents are investigating suspicious white powder sent to Sunset High School in Dallas, Whitt Elementary in Sacshe, Wylie High School in Wylie, Gulledge Elementary in Plano and Texas Instruments in Dallas.
Also on Monday, white powder discovered in letters caused scares at a gallery in New York City, a bank building in Birmingham, Ala., and a restaurant in Washington, D.C.
NBC 5 has learned the letter sent to the Neue Gallery in Manhattan was postmarked in Grapevine and contained a cryptic message: “Law enforcement in this country is corrupt.” It also made reference to the “Nazi police.”
A series of mailings sent from North Texas since 2008 -- hundreds of letters in all -- have challenged U.S. postal inspectors and FBI agents.
The first letters were sent to governor’s offices around the country and U.S. embassies around the world from Spain to South Korea.
All the postmarks were stamped “Dallas” or “North Texas.”
Since then, hundreds more letters have turned up at schools, defense contracts and airports.
Many of the early letters contained the same confusing, cryptic message about "Al Qaeda, FBI in America,” NBC 5 has reported.
The envelopes included return addresses, but they didn't give agents much of a clue. They were the addresses of current or former FBI offices in Texas.
U.S. Postal Inspector Amanda McMurrey in Fort Worth referred questions about Monday’s cases to the FBI.
In Dallas, FBI spokeswoman Lydia Maese confirmed agents were investigating the mailings but could not say if they were related.