The blaze was reported from the 15 storeyed building, which is around 50 metres high, on K G Marg near Connaught Place at around 6:20 AM and 32 fire tenders were rushed to the spot to douse the fire.
Till noon, the fire was not doused.
The fire broke out in the third floor of the building and it spread to the fourth floor.
Half a dozen guards, who were inside the building at the time of the incident, were taken out safely, fire brigade officials said.
However, one person is believed to be trapped inside the building.
Thick plumes of smoke were billowing out of the building and rescue workers were working hard to douse the fire which broke out apparently due to an electrical fault.
Police and fire brigade officials said they were yet to ascertain the cause of the blaze though they suspected it to be due to a short circuit.
"There was a lot of smoke. The smoke blackened the sky," Kamal, an eyewitness, said.
Police has blocked traffic on K G Marg from Outer Circle of Connaught Place to Tolstoy Marg intersection on K G Marg.