Authorities in Saitama Prefecture, north of Tokyo, are transferring sewage water to a nearby river to rescue a truck driver who is trapped in a road sinkhole.

They have been pumping up the water to stop it from flowing into the hole, and began discharging it into the river late Wednesday night.

Prefectural officials say the water is being disinfected with chlorine before being released into the river, which is not used for tap water.

The road collapse occurred on Tuesday at an intersection in Yashio City. A truck fell into the hole and its 74-year-old driver remains trapped. The hole was initially 10 meters wide and 5 meters deep.

The officials attribute the collapse to the rupture of a pipe that leaked the sewage water. Another sinkhole was created nearby, probably because leaking water eroded mud underground.

The two holes were connected early on Thursday when the soil between them collapsed. The officials say there could be more cave-ins.

Rescue personnel are using small machinery to remove mud from the sinkhole so they can pull the driver out. They have also used a drone to look inside the hole.

Officials say the rescue personnel face risks from a possible follow-up disaster. The driver's condition remains unknown.

The officials say the broken sewage pipe cannot be repaired anytime soon, and the impact of the accident will drag on.

They are planning to discharge sewage water into two more rivers to prevent it from filling up the hole.

They are also urging people who live near the upper reaches of the sewage system to minimize their water use.