<p class="title">An envelope containing an "unknown substance" was opened today at a US base near Washington, leaving 11 people sick, including military personnel, officials said.</p>.<p class="bodytext">The envelope was received at Joint Base Myer-Henderson Hall, leading to an evacuation of the building, the US Marine Corps said in a statement.</p>.<p class="bodytext">Base officials "are coordinating with local HAZMAT teams and FBI. Several Marines are receiving medical care as a result of this incident," the statement read.</p>.<p class="bodytext">"No additional details are available at this time as the investigation is ongoing."</p>.<p class="bodytext">The Arlington Fire Department tweeted that "11 people started feeling ill after letter was opened in consolidated admin building."</p>.<p class="bodytext">CNN reported that a corporal, gunnery sergeant and a colonel complained of a "burning sensation" on their hands and face.</p>.<p class="bodytext">Marine spokesman Major Brian Block said it was too soon to say whether the incident was being considered a terror attack.</p>.<p class="bodytext">"It's way too early to start speculating on any of that, we have to wait and let the investigators do their jobs," Block told AFP.</p>.<p class="bodytext">Joint Base Myer-Henderson Hall overlooks Arlington Cemetery just across the Potomac River from Washington.</p>
<p class="title">An envelope containing an "unknown substance" was opened today at a US base near Washington, leaving 11 people sick, including military personnel, officials said.</p>.<p class="bodytext">The envelope was received at Joint Base Myer-Henderson Hall, leading to an evacuation of the building, the US Marine Corps said in a statement.</p>.<p class="bodytext">Base officials "are coordinating with local HAZMAT teams and FBI. Several Marines are receiving medical care as a result of this incident," the statement read.</p>.<p class="bodytext">"No additional details are available at this time as the investigation is ongoing."</p>.<p class="bodytext">The Arlington Fire Department tweeted that "11 people started feeling ill after letter was opened in consolidated admin building."</p>.<p class="bodytext">CNN reported that a corporal, gunnery sergeant and a colonel complained of a "burning sensation" on their hands and face.</p>.<p class="bodytext">Marine spokesman Major Brian Block said it was too soon to say whether the incident was being considered a terror attack.</p>.<p class="bodytext">"It's way too early to start speculating on any of that, we have to wait and let the investigators do their jobs," Block told AFP.</p>.<p class="bodytext">Joint Base Myer-Henderson Hall overlooks Arlington Cemetery just across the Potomac River from Washington.</p>