Firefighters in Karachi began searching on Monday for more than 60 missing people after a massive fire destroyed a shopping mall in Pakistan’s most populous city, while the death toll from the disaster rose to 11.

The fire started late on Saturday at the sprawling, multi-storey Gul Plaza shopping centre in the city’s business district and burned for more than 24 hours, hampering rescue efforts in the densely packed area.

After more than 24 hours of firefighting, crews moved to cooling and debris-clearing on Sunday, although concerns grew that more victims could still be trapped inside.

Police surgeon Dr. Summaiya Syed told Reuters the death toll had risen to 11, while Karachi Mayor Murtaza Wahab said on Sunday that more than 60 people were still missing.

Firefighters said the lack of ventilation in the building, which houses more than 1,200 shops, caused thick smoke to fill the mall and slowed efforts to reach people trapped inside.

“It appears to have been caused by a circuit breaker,” Sindh province police chief Javed Alam Odho told reporters at the site on Sunday, adding that the layout of the market and the presence of flammable materials such as carpets and blankets caused parts of the fire to continue smouldering.

By Sunday evening, large sections of the building had collapsed, leaving twisted metal and debris strewn across the street, along with fallen air-conditioning units and shop signboards. Rescue workers warned that the remaining structure was unstable and could collapse further.

According to rescue services, authorities received the first emergency call at 10:38 p.m. (1738 GMT) on Saturday, reporting that ground-floor shops were on fire. By the time firefighters arrived, the flames had already spread to the upper floors, engulfing much of the building.

Shopkeepers and residents told local media that a delayed response and shortages of water and equipment had hampered early firefighting efforts, fuelling anger among traders who said decades of livelihoods had been wiped out.