CNN) -- At least one person was injured Monday after a person fired shots inside the Washington Navy Yard, the U.S. Navy said.
An official told CNN's Barbara Starr that "several" people sustained injuries, according to phoned-in reports from the building.
The incident occurred at 8:20 a.m. when several shots were fired inside the headquarters for Naval Sea Systems Command in southeast Washington, D.C. An "active shooter" remained inside the building, the Navy said.
The Navy first informed the public of the incident in a Twitter message.
Shooting at Washington Navy Yard
Emergency personnel, the FBI, U.S. Capitol Police and local D.C. police responded to the shooting. Some people are being evacuated and others are sheltering in place.
The headquarters -- the workplace for about 3,000 people -- is the largest of the Navy's five system commands.
It has a fiscal year budget of nearly $30 billion,
"With a force of 60,000 civilian, military and contract support personnel, NAVSEA engineers, builds, buys and maintains the Navy's ships and submarines and their combat systems," the Navy said.