Hopes faded for a 74-year-old man in Japan whose truck was swallowed by a sinkhole as rescue efforts entered their third night Thursday. The chasm widened, and locals were urged to limit water use to aid the operation.

Authorities have asked 1.2 million people to reduce water consumption to prevent leaking sewage from hindering the rescue. Rescuers have not made contact with the truck driver since Tuesday afternoon.

The sinkhole opened suddenly at an intersection in Yashio, north of Tokyo, during Tuesday’s rush hour, swallowing the truck. Initially about 10 meters wide and 6 meters deep, the hole has since merged with another.

"At around 2:30 am (on Thursday), the two holes became one, and with risk of another landslide or collapse of roads, we've been unable to use heavy machinery," a fire department official told AFP.

Rescue efforts have been severely hampered by unstable ground around the hole. Water has also been seeping in.

The sinkhole and its vicinity remained cordoned off Thursday evening, surrounded by an array of factories that make the area something of an industrial hub.

"I always use that intersection to commute, which makes me think I could've been there when it happened," Hiromasa Saito, a worker at a nearby metal processing factory, told AFP. 

"We're being told by the company to cut back on water, so we're washing our hands less," the 50-year-old added.

Authorities suspect the sinkhole was caused by corroded sewage pipes beneath the intersection. The pipes allowed soil to flow in, hollowing out the space below and weakening the asphalt.

The punctured pipes "potentially allowed the surrounding soil to flow in and the space under the ground to hollow out", Daisuke Tsutsui, a Saitama prefectural official, told AFP. 

"When the hollow got big enough, the asphalt on it could no longer withstand the weight of its own and cars passing by, which possibly led to the hole emerging," Tsutsui said.

Rescuers have been working around the clock to reach the truck driver.