Firefighters in Pakistan’s largest city were fighting to extinguish a massive blaze on Sunday that has killed six people and reduced parts of a shopping mall to rubble in Karachi’s historic downtown.

Videos showed flames rising from the building as firefighters laboured through the night to stop the fire from spreading in the dense business district. Hundreds of people had gathered around the building, including distraught store owners whose businesses had turned to ash.

The fire erupted on Saturday night, with rescue services receiving a call at 10:38 p.m. (1738 GMT) reporting that ground floor shops at Gul Plaza were ablaze.

“When we arrived, the fire from the ground floor had spread to the upper floors, and almost the entire building was already engulfed in flames,” Rescue 1122 spokesperson Hassanul Haseeb Khan told Reuters.

Police surgeon Dr. Summaiya Syed said six bodies had been brought to Karachi’s Civil Hospital and 11 people who had been injured, adding that police were “invoking mass disaster protocols”.

Images of the mall’s interior revealed the charred remains of stores and a bright orange glow as flames continued to rise throughout the building.

Local media reported that parts of the building had started to collapse and rescue officials feared the whole structure could come down.