A fire official said the flames were reported at around 4.45 PM and 10 firetenders were rushed to the spot. Later, 22 more tenders were deployed.
The blaze has now been partially doused and operations are on.
A senior police offcier said the fire started in the server room on the first floor of the five-storey building on Bahadur Shah Zafar Marg. The people present there managed to get out in time, he said.
"It is suspected that there was some problem in the cooling system and extra heat was generated. It is suspected that it was the trigger for the fire that spread quickly through the first floor," he added.
A major fire had engulfed parts of the building's top floor in May last year.