The firefighters are trying to rescue people stuck in the chemical factory
According to local media, 25 others were still trapped inside the building located in the Mehran town of Karachi, the provincial capital of southern Sindh province.
TV footage showed firefighters dousing the flames and ambulances transporting victims, Associated Press reported.
The cause of the fire was not immediately known.
The spokesperson for the provincial government Murtaza Wahab told reporters that the firefighters had almost extinguished the fire.