Four people have been injured in a fire that broke out in the US State Department's headquarters in Washington DC Saturday.

State Department spokeswoman Victoria Nuland informed a work crew was engaged in "routine maintenance in the mechanical area of the main State Department building" when flames broke out in the ductwork on the 7th floor.

District Fire Department spokesman, Lon Walls, is quoted saying that one worker had life-threatening injuries, two others had serious, but non-life-threatening injuries, and the fourth sustained a knee injury falling off a ladder. All three were taken to Washington Hospital Center.

Walls further reported that workers were able to put out the fire with handheld extinguishers before firefighters arrived. According to the Washington Post, he has said the fire "appears to be accidental," though it was still under investigation.

The building was briefly evacuated and then reopened. Very few people were inside over the four-day Thanksgiving holiday.