(HOUSTON, TX) -- The F.B.I. has taken the lead in investigating powder-filled envelopes at several schools in Houston, Texas. Seventeen schools have received the envelopes since Friday. Preliminary testing shows the powder to be corn starch, but authorities are taking it very seriously, treating it as a terrorist threat.
The U.S. Postal Service is working to prevent similar packages from getting to more schools. Sixteen of the seventeen schools that have received the standard, business-size envelopes have names beginning with the letters A and B. That may suggest someone working through the alphabet and Houston Independent School District officials say they are checking with all the other schools.
It will take two weeks to complete tests on the powder and if it can be determined where it came from and who sent it, federal charges could follow.
Copyright ABC News Radio