Many are feared buried under the debris, senior officials said.
The incident took place around 11.20 AM, following which disaster management teams, fire brigade and police teams rushed to the spot and launched a rescue operation, they said.
It was an old residential building near the Church Mission police post in Lahori Gate.
The rescue mission is underway, a police official said adding that the identities of the deceased and injured persons could not be ascertained yet.