(CNN) -- For nearly six years, hundreds of letters, most containing a suspicious white powder, were sent through the mail, addressed to President Barack Obama, members of Congress, hotels near the Super Bowl, schools, companies and others.
And over that time, no one was arrested -- until Monday.
That's when Hong Minh Truong, 66, of the Dallas suburb of Rowlett, was picked up by the FBI and the Postal Inspection Service.
According to a law enforcement complaint filed in federal court, more than 500 hoax letters were mailed since 2008 from the North Texas area to cities across the United States and to U.S. Embassies abroad.
The Justice Department said none of the letters contained any poison or toxins, but they still required an emergency response to determine whether they were harmful. Some letters did not contain any powder.
The language used in the letters as well as the method for sending them indicate that Truong was responsible, authorities said.
The Justice Department said the letters were sent to government offices, aerospace companies, schools, day care facilities, and hotels in the vicinity of this year's Super Bowl.
Separately, multiple sources familiar with the matter told CNN the letters were also addressed to Obama and members of Congress.
CNN's Evan Perez, Shimon Prokupecz and Jason Morris contributed to this report.