WASHINGTON -- ATF headquarters had to evacuate Thursday afternoon after an employee opened an envelope with a suspicious liquid substance inside.

DC Police were called to 99 New York Avenue, Northeast around 2:21 p.m after the staffer opened the suspicious package. HAZMAT tested the substance in the envelope and it was cleared.

Officials said it will be sent to a lab for further analysis.

DC Fire and EMS said they were dispatched to the scene just before 2:30 p.m. to assist in the investigation.

HAZMAT officials said the liquid is clear but will undergo further testing.

This is a developing story.