Authorities in Saitama Prefecture announced Wednesday that they have discovered what appears to be the cabin of a truck inside a sewer pipe downstream from the site of a road collapse that swallowed the vehicle last week.

However, the truck’s 74-year-old driver remained missing as of Thursday morning. The search has continued to be challenging due to the presence of hydrogen sulfide and fast-flowing sewage water inside the pipe, according to prefectural officials quoted by NHK.

A drone probe was deployed after officials suspected an obstruction in the sewer system. It located a deformed white metal mass about 100 meters downstream from the collapse site.