A sinkhole opened up beneath a major road in downtown Fukuoka on Tuesday morning, disrupting traffic, power transmission and banking systems as authorities scrambled to evacuate surrounding areas at risk of more cave-ins.

The Fukuoka police and City Hall said they had not received any reports of injuries but blocked off nearby areas as a safety precaution.

The road apparently caved in at around 5:15 a.m. at an intersection near JR Hakata Station, according to Fukuoka City Hall.

The intersection is near an area where construction was underway to extend the Nanakuma subway line. City officials said the sinkhole was likely caused by water flowing into tunnels at the site.

While there were dozens of workers at the site, all fled in time and were confirmed safe, they added.

Work to extend the Nanakuma Line has also been linked to a smaller sinkhole that emerged in the same district in October 2014.

One expert speculated that the sinkhole was caused by multiple factors in addition to the construction work, such as high levels of groundwater and deterioration of the sewer system.

Nihon University professor Satoru Shimobe, who specializes in geoenvironmental engineering and geotechnical engineering, said a large portion of today’s sewer networks, which cover some 460,000 km nationwide, was built in the 1970s, when Japan was undergoing rapid economic growth. Most of the pipelines set underground have deteriorated over the years, he said.

“It is a growing social issue,” he said, adding that the number of sinkhole incidents rises every year and is hovering at a rate of around 4,000 to 5,000 annually.

He said he believed heavy rainfalls in recent years had affected the already aging piping systems in the sewerage network in Hakata, which is a sea port with a high level of underground water.

TV footage showed the hole filled with water from underground channels. As of 6 p.m., the sinkhole had expanded to 30 meters long, 27 meters wide and 15 meters deep.

The city evacuated buildings, including several offices near the site at 9:45 a.m., saying there were signs the cave-in could cause buildings to collapse.

Police also told nearby offices and households not to use gas, fearing gas leaks.

Saibu Gas Co. said it has suspended its supplies to areas in the vicinity of the sinkhole.

The Bank of Fukuoka said its online systems appeared to have been disrupted by the accident.

Fukuoka airport also temporarily experienced blackouts, forcing ticket machines to stop working briefly.

Some 800 households were affected by blackouts early in the morning, but power was restored gradually, reducing the number of affected households to only 14 as of 3 p.m., according to Kyushu Electric Power Co.

“When I came to the office, police instructed us to get out of the building. It seems like I need to stay at home for now,” said Tsuyoshi Ito, 48, who works near the site.

Another person who was in a nearby building said: “The lights suddenly went out and there was a big heavy sound. When I went out, there was a huge hole.”

In the past few years, there have been cases in which underground construction work has caused roads to cave in.

In October 2014, about three meters of road in the city of Fukuoka caved in several meters near where construction to move sewage was underway. No one was injured.

Last December, a sidewalk located in front of a building construction site in the city of Nagoya caved in about 5 meters. No one was injured but the site was about 300 meters from Nagoya Railroad Co.’s Nagoya Station. A construction failure in a concrete wall between the sidewalk and the construction was blamed for the cause.

Also in Nagoya in June, several roads and part of a park sunk in near a site where construction was underway to build a tunnel to store rainwater.

KEYWORDS Fukuoka, sinkhole