FBI Investigating White Powder Letters Sent to Washington D.C. Schools

May 5, 2011 — -- Suspicious letters containing white powder were sent today to at least 20 public schools, triggering an investigation by the FBI and the Washington Fire Department.

"We've got 10 locations that we've responded to. We are in the process of collecting the letters. They'll be taking them to a certified state lab for testing," said Andrew Ames, spokesman for the FBI Washington Field Office.

At least four of the 10 schools that received the letters have been cleared. Elementary, middle and high schools throughout the district received the letters.

The first letter was reported at Terrell Elementary School this afternoon.

Law enforcement sources told ABC Affiliate WJLA that all of the letters appeared to contain the same contents. Some were sent from Texas, WJLA reported.

The envelope sent to the School Without Walls stated "al quaida, fbi, usa" and was from North Dallas, Texas, WJLA reported.

None of the letters tested so far have been hazardous, Ames said. No one has reported any illness or injury.

The four schools that have been cleared are M.C. Terrell/McGogney Elementary School, Brown Middle School, Powell Elementary School and Martin Luther King Elementary School.

It's unclear if any schools were evacuated. Calls to D.C. Public Schools were not returned.

ABC News' Jason Ryan contributed to this report.