The sinkhole has expanded, but Japan has yet to rescue the person who fell in.

Japanese rescuers on January 31 continued to dig a slope down into a sinkhole in Yashio, a city in Saitama Prefecture, to bring in heavy machinery to search for the driver missing since his truck was swallowed by the sinkhole on January 28.

The hole was originally 10 meters wide and 5 meters deep, but has now expanded to 40 meters, nearly the length of an Olympic swimming pool, and 10 meters deep. Yashio officials said the hole's growth may have been due to corrosion in the sewage system.

"This is an extremely dangerous situation," local police chief Tetsuji Sato said at the scene, where dozens of rescue workers were working around the clock.

"We are building a slope to access the sinkhole from a safer location to bring in heavy machinery," he said on January 30, noting that groundwater had leaked inside and the hole "continued to collapse."

They have not been able to contact the 74-year-old driver since midday on January 28, when the truck’s cab was covered in rubble. Saitama officials hope to complete the 30-meter-long ramp by January 31, but a local official said it could take longer.

The 1.2 million residents in the area have been asked to reduce bathing and washing to avoid sewage leaks that would put a strain on rescue efforts. "It's difficult to reduce toilet use, but we've asked people to minimize water use," an official said.

Takuya Koroku, 51, a local factory worker, said he "felt it was unusual that the search was taking so long. I wondered when he would be rescued."

"I'm scared to go near it," Koroku said.