Authorities say five workers are confirmed dead after the collapse of a subway tunnel under construction in the northeastern Chinese city of Qingdao.

The body of the last worker listed as missing was recovered Saturday, five days after the tunnel crumbled with the workers inside. The cause of the collapse remains under investigation.

China has been rapidly building and expanding mass rapid transit systems to accommodate growing urban populations and keep the slowing economy growing through government fiscal stimulus and infrastructure projects.

Partly as a result, China has suffered a steady stream of industrial accidents this year, including building and worksite collapses. In March, 78 people were killed in a blast at a chemical plant in the country’s east.