News reports say there was a fire in the mechanical room at the West Wing early Saturday. There are no injuries reported.
Officials say a transformer in the mechanical room overheated.
Smoke triggered an alert at the White House but all fire engines have left, according to various news reports.
Reporters and photographers were evacuated from the White House press room because of the smoke.
The journalists were sent outside shortly after 7 a.m. while firefighters inspected the West Wing. They were allowed back into the building about an hour later.
White House officials say President Barack Obama and his family were not affected by the incident.
The Associated Press contributed to this story.