Some lawmakers and their staffs were kept out of their offices Thursday morning while firefighters put out a small blaze on the roof of a congressional office building.

Construction workers are being blamed for the fire on the roof of the Rayburn House Office Building (search).

"Roofers using an open flame or other metal cutting device likely started it," said Alan Etter, a spokesman for District of Columbia Fire and Emergency Medical Services.

The call first came in about 6 a.m. for the report of a smell of smoke in the building, Etter said. Firefighters who responded to the scene initially determined a burned out motor in a fan on the roof was to blame.

A short time later, flames were seen on the roof. Further investigation determined the roofers were to blame.

"The fan is somehow involved," Etter said. An investigation was continuing into the cause.

Several roads were shut in the area, snarling rush hour traffic -- but were reopened a short time after the fire was put out. Most employees were allowed to return to the building, according to fire officials.

"A few rooms in the top floor of the southeast part of the building remained closed," because of some fire damage, Etter said.

No one was hurt in the blaze.

At least one committee hearing scheduled for 9:30 a.m. was delayed an hour to allow people time to get ready.

Among those temporarily shut out was Sen. Charles Schumer (search), D-N.Y., who exercises in the lawmakers' gym in the building.

"It's not like I escaped certain death," Schumer said. "I escaped certain exercise."