The NID database server is safe, according an EC official.
“It’s a small fire,” duty officer Farhad Ul Alam said and added they were yet to extinguish it.
“Smoke is still billowing,” he said at 12:30am on Monday.
Six more units and military personnel, who are trained to fight fire, joined in later.
The fire was brought under control after around an hour, officials said.
No casualties were reported.
The fire “might have damaged some EVMs”, EC NID wing Director General Brig Gen Saidul Islam said.
In 2015, a fire in a building next to the Islamic Foundation in the same area disrupted NID services when the related wing was situated there. It was later moved to the new headquarters “Nirbachan Bhaban”.
Saidul said the fire was brought under control within an hour. “We don’t fear any big damage,” he said.
They initially suspect the fire originated from electric short circuit, the EC official said.
Fire Service Deputy Director Debashish Bardhan said the EC and the Fire Service have formed two committees to investigate the incident.
The three-strong EC committee led by Additional Secretary Mokhlesur Rahman has three days to report while the Fire Service committee with as many members got two weeks.
Paper cartons stored in the basement besides EVMs caused more smoke, the fire service official said.
Election Commissioner Mahbub Talukdar visited the building around 1:30am.
On being asked by a reporter, he said he did not know whether the fire extinguishers of the building were operational or there was any flaw in the fire safety system.
“The investigation committee will find it out,” he said.
The election commissioner hailed the firefighters for their efforts to control the fire “quickly”.
He said Chief Election Commissioner KM Nurul Huda was abroad but was in constant communication with officials over the incident.