Some more people are feared to be trapped under the debris, police said.
Rescue teams of Delhi Fire Services (DFS), disaster management and the local police personnel were immediately rushed to the spot as the building fell like a house of cards around 7.45am, fire department officials said.
Deputy commissioner of police (north) Sindhu Pillai said the injured persons have been rushed to the Bara Hindu Rao Hospital for medical attention.
"A rescue operation is on and we believe some more people are trapped under the debris," she said.
The deputy commissioner said the building was very old and in a dangerous condition. A few days ago, the police had written a letter to the Municipal Corporation of Delhi, requesting them to inspect the building. The inspection, however, was yet to be conducted.
The owner of the building has been booked for negligence. A case under various sections of the IPC has been registered against him at the Bara Hindu Rao police station.