A gas explosion has torn through an apartment building in Pakistan’s largest port city of Karachi, killing at least 13 people, including women and children, and injuring several others after part of the structure collapsed, police and rescue officials said.

The explosion happened on Thursday in a residential area of Karachi, the capital of the southern Sindh province, according to local police chief Rizwan Patel.

Rescuers were still removing rubble to search for any survivors trapped under the debris, he said. The search-and-rescue operation was ongoing.

Most houses and apartment buildings in Karachi, like elsewhere in Pakistan, are supplied with natural gas for cooking. However, many households also rely on liquefied petroleum gas cylinders because of low natural gas pressure.

In July, a gas explosion following a wedding reception at a home in Pakistan’s capital, Islamabad, killed eight people, including the bride and groom. The blast occurred as guests had gathered to celebrate the couple, authorities said.