The brand new Capitol Visitor Center has been evacuated after an alarm sounded, and several emergency vehicles are on the scene.
It's not clear yet what tripped the alarm or whether this is a real emergency. The main part of the Capitol remains unaffected by this evacuation. The CVC is now the main facility in the Capitol for tourists, so this may disrupt activities in the building for awhile.
The Crypt is on the scene and will update as more information becomes available.
UPDATE: Everything has been cleared and apparently welding work in the CVC caused the smoke and the alarm. The CVC is preparing to reopen.