DALLAS (CBSDFW.COM/AP) — A North Texas man faces up to 25 years in prison for mailing hundreds of white powder hoax letters to schools, government offices and U.S. embassies.

Hong Minh Truong pleaded guilty Friday to five counts of false information and hoaxes in an indictment stemming from more than 400 letters.

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Federal prosecutors in Dallas say the 67-year-old Rowlett man remains in custody pending sentencing this fall.

Truong was arrested last July and linked to letters mailed since 2008. Some of the initial letters had Dallas postmarks and others were mailed from sites across North Texas.

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The letters were sent to U.S. government offices, schools, daycare, aerospace companies and hotels near Super Bowl XLVIII in New Jersey.

Last year Dallas FBI Special Agent in Charge Diego Rodriguez said, “While it was determined that the mailings did not contain toxins or poisons, each incident required a field screening of the letter’s contents, which cost taxpayer dollars and diverted first responder resources.”

Investigators say an IP address associated with Truong was identified after 28 schools in Boston received hoax letters in mid-2013.

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