DALLAS — Federal authorities have arrested a Texas man accused of sending more than 500 hoax letters that contained a white powder to schools, U.S. government offices and other locations around the world.

Hong Minh Truong made his initial appearance in Dallas federal court on Monday following his arrest earlier in the day.

The 66-year-old is charged with false information and hoaxes. Federal authorities say none of the letters Truong is accused of sending since 2008 contained toxins or poisons.

A judge ordered that Truong be held in custody until a detention hearing on Aug. 4.