Feb. 27 (UPI) -- Nearly a dozen people fell ill Tuesday after an unknown substance was found in an envelope at a military base in Virginia, the Arlington County Fire Department said.
The fire department said 11 people started feeling ill after the letter was opened at Joint Base Myer-Henderson Hall in Arlington.
Three patients were transported to the hospital in stable condition to be evaluated furter.
The U.S. Marines said it took "immediate preventative measures" by evacuating the building.
"Base officials are coordinating with local HAZMAT teams and FBI. Several Marines are receiving medical care as a result of this incident," the Marines said.
All patients were guided outside of the building and have been decontaminated, the Arlington County dispatch said, according to WUSA9.
Hazmat crews prepared to enter the building and examine the letter.