Central Japan Railway Co. (JR Central) has unveiled the inside of a tunnel under construction in Gifu Prefecture for use as part of its ultrafast maglev train line, scheduled to go into service in 2027.

A section of the Hiyoshi tunnel that is currently being drilled was shown to reporters Tuesday. It was the first time JR Central had shown the inside of a tunnel to be used for the Chuo Shinkansen line.

The mountainous construction zone of Minamigaito in the city of Mizunami is 7.4 kilometers long and 14 meters wide.

The construction of the tunnel started in December 2016, and the drilling work began in October last year.

Roughly 890 meters of the 8-meter high tunnel had been excavated as of Tuesday, with workers burrowing through at a pace of some 6 meters per day. The inner wall of the tunnel, lit by lights, was coated with concrete.

Two maglev train lines in both directions will run through the tunnel.

At the construction site, a 2-km-long conveyor belt has been used to carry dirt from the drilling process out of the tunnel. The site is the only one among the construction sites for the maglev line that has a conveyor belt.

By using the equipment, “we can reduce environmental burdens, noise and vibrations caused by the dirt transportation work, compared with use of trucks,” said Satoru Kato, a JR Central official.

The construction of the maglev line, however, hasn’t been proceeding entirely smoothly.

In Shizuoka Prefecture, where full-scale construction has yet to begin, there is lingering local concern about a possible decrease in water in the Oi River, a lifeline to local residents, that could be caused by drilling a long tunnel under the river.

The transport ministry is working as a go-between to convey local worries to JR Central. Last week, ministry officials had a discussion on the matter with Hideyuki Harada, the mayor of Fukuroi, which could be affected by the maglev construction.

In addition, some shady business practices have been uncovered in the construction of the maglev line.

Earlier this year, the transport ministry ordered two major contractors, Obayashi Corp. and Shimizu Corp., to temporarily suspend part of their business operations after they were fined last year by a Tokyo court for rigging bids for construction work.