The Department of Commerce headquarters in downtown Washington was evacuated Thursday afternoon after construction dust triggered a fire alarm, the fourth such incident in 11 days.

The alarm at the Herbert C. Hoover Building at 1401 Constitution Ave., N.W., was triggered at 1:08 p.m. by construction dust related to ongoing renovation work, according to a Commerce Department statement. After the building was cleared by the fire department, workers were able to return shortly after 2 p.m.

One worker described Thursday’s evacuation as “disruptive, but not disastrous.”

All the recent evacuations are related to the renovation work, the statement said.

On July 9, a short circuit caused smoke that forced the building’s evacuation for about 40 minutes, shortly before noon. Workers had no sooner returned to the building than the alarm went off again, caused by a failure of the system to fully reset itself, prompting another short evacuation.

The following day, a similar false alarm forced workers to evacuate again for about five minutes.

Renovation of the historic 1932 building, which has 3,300 rooms and more than 1.8 million square feet of office space, began in 2007 and is scheduled to be completed in 2021.

The project includes replacing aging machinery, as well as electrical, ventilation and other old systems.

“There has been an increase in the number of false fire alarms that occur during renovation efforts due to the nature of the work being done,” the department’s statement said. “The department is actively working to put in safeguards that minimize the amount of false fire alarms caused by renovation activities, thereby reducing the number and length of employee evacuations during such alarms.”