The President’s residence has been put on lockdown after the loud noise was heard moments before Barack Obama and his family were due to take off by helicopter on the grounds.
Secret Service agents immediately moved press into a briefing room and locked the doors.
Local reports said bomb-sniffing dogs have alerted officers to a vehicle near the White House.
It is understood the explosion was a food truck on fire.
A video from near the scene shows a thick plume of black smoke billowing high into the air and down the street.
A report said: “Lockdown continues, although it doesn’t appear as though there’s a high level of consternation among Secret Service walking outside.”
The White House is yet to confirm more details with the media.
Obama and his family were about to depart by helicopter to Andrews Air Force Base to board Air Force One and travel to Selma, Alabama, to commemorate the 50th anniversary of a civil rights march.