Investigators are investigating an obvious hazardous substance situation at Myer-Henderson Hall Joint Base in Ft. Myer, Virginia, after a number of people felt ill after opening a letter, officials said.
Arlington Fire, one of the units that responded to the scene, said that "11 people felt sick after opening the letter" administration building. Three patients were hospitalized and reported to be in a stable condition.
According to the US Marines, employees have taken "preventative measures" and evacuated people from the building.
"Several Marines receive medical care incident," they added.
The suspicious substance has been collected by authorities and the FBI is on its way, officials said.
This is an evolving story; Please check the updates.
Fox News & # 39; Lucas Tomlinson and Jennifer Griffin have contributed to this report.