The city of Bungo Ono, Oita Prefecture, has seen cracks in the ground in 81 locations, leading the municipal government to warn nearby residents of possible landslides and urge them to evacuate.

The reason for the cracks is unknown, but the use of groundwater might have contributed, according to local officials.

According to the city, residents and municipal officials have seen 81 cracks on roads and in rice paddies in an area encompassing 400 by 300 meters since May 16 in the Asajimachi-Watada district. The deepest crack is 80 meters long, 30 cm wide and 1.5 meters long.

While nobody has been injured, one household has seen a crack on its property.

The city has issued an evacuation advisory to 10 residents in three households. Ikuko Anan, a 72-year-old resident who was among the affected, looked worried as she prepared to evacuate.

"I hope to return to my home soon," she said.

The cracks are seen in an intermediary area between a plain and mountains and are dotted by rice fields. The area experienced a landslide in 1964 and the central and city governments have designated it as an area in danger of further damage.

"We will keep an eye on the area, and will consider offering residents alternative housing at a prefectural-run apartment if their evacuation is prolonged," Oita Gov. Katsusada Hirose told a news conference on Monday.