Emergency workers in Japan have begun building a ramp to try and reach a 74-year-old truck driver who has not been heard from since his vehicle was swallowed by a sinkhole this week.
The cavity has expanded to 40 metres across, almost the length of an Olympic swimming pool, since opening up in a city just north of Tokyo on Tuesday morning, officials said.
The growing hole could be the result of corroded sewage pipes, according to authorities in Yashio.
"It is an extremely dangerous condition," local fire chief Tetsuji Sato told reporters at the traffic intersection where dozens of rescuers have been working around the clock.
He added: "We are planning to construct a slope (to access the hole) from a safer spot so that we will be able to send heavy equipment."
He added that groundwater was leaking inside and that the hole was "continuing to cave in".
No communication has been had with the driver since around midday Tuesday, with soil and other debris now covering the cabin of his lorry in Yashio.
Eroding walls and falling debris
The punctured pipes "potentially allowed the surrounding soil to flow in and the space under the ground to hollow out", Saitama prefectural official Daisuke Tsutsui said.
Authorities hoped to complete the 30-metre slope today, but a local official said it may take several days.
The operation has been aggravated by the inner walls of the hole - now around 10 metres deep - continuing to erode, preventing rescue workers from staying inside it for long.
Initially, the hole was around five metres in diameter, but it has since combined with a much larger cavity that opened during the rescue operation on Tuesday night.
As the sinkhole has expanded, heavy chunks of asphalt have occasionally fallen in, preventing rescue workers from going near the chasm.
This has also made it dangerous to place heavy machinery nearby.
The 1.2 million people living in the area have been asked to cut back on showers and laundry to prevent leaking sewage from making the operation even more difficult.
"Using toilets is difficult to refrain from, but we are asking to use less water as much as possible," an official said.
Some sewage water in the area was collected and released to a nearby river to reduce the runoff into the hole.
Local factory worker Takuya Koroku said: "It feels rather abnormal that the search is taking this long. I wonder if he could've been saved much sooner."
"I'm scared to go nearby," the 51-year-old added.
Read more: Rescue operation after truck falls into sinkhole in Japan
