Firefighters responding to another white powder letter Wednesday.
The latest letter was received at the Mi Escuelita preschool on the 4200-block of Maple Avenue just off the Dallas North Tollway in Dallas.
The powder was discovered at about 9 a.m. when a member of the administrative staff was opening the mail on the second floor. The woman put the envelope in a plastic bag and is now being screened at a local hospital.
One classroom with 18 children between the ages of 3 and 4 was evacuated as a precaution. Another class with 54 children remains in session. None of the children were exposed to the powder.
“I don’t understand what they get out of this. I don’t know what they derive from scaring teachers and children. They’re small, small children. I would question what the motive was. I don’t understand it. If it’s just to cause havoc, I wish you had something better to do with your life,” said Gayle Nave, executive director of Mi Escuelita.
Officials have not said if there was a letter inside the mailing and have not yet revealed the material found. The investigation was initially performed by Plano firefighters because the Dallas HAZMAT team was undergoing training in Fort Worth.
On Tuesday, a half-dozen white powder letters were received in Irving, Garland, Dallas and Mesquite. Tuesday's letters were sent to early development schools, a church and a day care.
Dallas Fire-Rescue is turning the investigation over to the FBI.
NBC 5's Kendra Lyn contributed to this report.