A mountain of rubbish collapsed at a landfill in the central Philippines on Thursday, killing a 22-year-old woman and leaving more than 30 people missing, authorities have said.

Rescuers pulled 12 injured sanitation workers from debris at the Binaliw Landfill in Cebu City, who were later hospitalized.

Many of the missing are believed to be workers at the landfill. The mayor of Cebu told news outlet ABS-CBN that it may be difficult to reach survivors because of the potential for further collapse.

The cause of the collapse is still unclear, but Cebu City councillor Joel Garganera said it was likely the result of poor waste management practices.

Some 300 people from various government agencies and civilian groups have been deployed to the privately-owned landfill. Several excavators, ambulances and fire trucks have also been seen on site.

All response teams remain fully engaged in search and retrieval efforts to locate the remaining missing persons, Cebu Mayor Nestor Archival said in a Facebook post on Friday.

This is not like other landslides that you can just excavate. If you pull from the top, the bottom is soft. Let’s say there is a person there, when you get the debris, it might get worse.

Families are anxiously waiting for updates on their loved ones trapped in the debris. One resident shared her heartache, while others expressed hope that their relatives were still alive.

The Binaliw landfill is about 15 hectares (37 acres), and such landfills are commonly found in major Philippine cities like Cebu, a key trading center in the Visayas.