The unsteady ground, with a hollow space below it, has hampered the rescue.
Television footage captured the asphalt road cracking and collapsing into the sinkhole, knocking down billboards.
Authorities have tried to save the driver by lifting his truck with cranes, but they could only recover the loading platform, leaving behind the cabin where the driver is believed to be trapped.
Officials have also tried without success to remove sediment and dig out the driver. They flew a drone into the hole to see if rescue workers could climb down, but no progress has been made.
Saitama prefectural sewer system official Jun Uehara said corrosion, possibly because of strong acid constantly passing through the system, might have created a hole in the pipe, causing soil above to fall in and create a large hollow space between it and the road.
No problem was found with the pipe during its last visual inspection, which is required every five years.
About 1.2 million residents have been asked to cut back on showers and laundry to prevent leaking sewage from further complicating the rescue efforts.
The Land, Infrastructure and Transport Ministry has ordered a nationwide inspection of sewer systems.
Most of Japan’s main public infrastructure was built during the rapid economic growth of the 1960s and 1970s. The sewage pipe in Yashiro is about 40 years old.
