The top floor of a three-storey commercial building in central Delhi's busiest and congested market lanes of Chandni Chowk collapsed inward on Monday following a massive fire, officials said, adding that an adjacent building was also damaged in the incident.

No casualty has been reported so far, they said.

After over 11 hours, the fire that broke out at the commercial building situated near Chandni Chowk metro station here Sunday night was brought under control, while the cooling operations are still underway, officials said.

"There was no one trapped inside the building as the shops and godowns were all closed. During the fire-fighting operation, one of the firemen sustained injuries, but he is fine now," a senior fire official said.

During the rescue operation, the fire fighters had to operate from the adjacent building as a massive fire had broken out and all the doors and windows were completely closed and there was no space to move inside, the official said.

The building comprised of combustible materials, mostly clothes stuffed inside the godowns and shops, he said.

Atul Garg, director, Delhi Fire Service said a call about the fire was received around 10.40 pm on Sunday.

He said six fire tenders were rushed to the site initially. He said the fire call was later upgraded to serious and a total of 40 fire tenders were sent to douse the flames. More than 150 fire personnel were deployed at the site.

Talking about the challenges faced by the fire fighters, Garg said since the lanes in Chandni Chowk are usually narrow and congested, it was difficult for the fire tenders to enter the lanes where the building was situated.

New fire tenders had to be brought in as there was no source of water supply.

Finally, the source of water was utilised from the available connections near Chandni Chowk metro station, he said.

The cause of the incident is suspected to be electrical malfunction, he added.