Witnesses and BNP leaders said the fire began to spread from the garbage dump at the narrow space in between the BNP office building and that of Victoria Hotel around 11:30am.
Seeing the smoke billowing from the fire, BNP Senior Joint Secretary General Ruhul Kabir Rizvi and other party leaders and activists hurriedly came out of their office.
They also put in efforts to douse the fire by pouring water with buckets.
At one stage, employees of Victoria Hotel put out the fire using extinguisher before firefighters reached the spot.
The power connection to the BNP office remained suspended for nearly 45 minutes following the incident.
Hearing about the incident, BNP standing committee member Gayeshwar Chandra Roy, joint secretaries general Syed Moazzem Hossain Alal, Khairul Kabir Khokon, and other party leaders also rushed to the scene.
However, Rizvi said the fire caused no damage as it was doused immediately.