Bai Gio Tunnel in Khanh Hoa Province and Chi Thanh Tunnel in Phu Yen Province have experienced landslides, which have cancelled many trains in the last two months.

Director of Phu Khanh Railway, Le Quang Vinh, said the tunnels had been used for a long time and had deteriorated badly.

"Additional landslides occurred while the tunnels were being restored, and the renovation work took more time," he said, adding that dozens of other century-old tunnels along the route have also shown signs of severe deterioration and faced the risk of landslides, especially during the rainy season.

Recent landslides at the Bai Gio Tunnel on the North-South Railway recently cost Vietnam Railway Corporation (VNR) VND50 billion (USD1.97 million) due to the disruption of services.

Vietnam Railways spent VND22.3 billion repairing the tunnel, while the remainder was due to loss of revenue.

During the 10-day suspension, the railway sector had to provide replacement transportation for over 30,000 passengers booked on 110 trains between Khanh Hoa and Phu Yen stations.

VNR said that repairs on the North-South railway had affected the firm's revenues. The corporation has proposed a 50 percent discount on infrastructure usage fees until all the repairs to the Hanoi-HCM City railway line are completed.

The Chi Thanh Rail Tunnel in Tuy An District in the southern central province of Phu Yen also experienced a landslide on May 21. Work to consolidate the tunnel was already underway when the landslide happened. Many trains on the route have been cancelled, and workers are still doing repair work, which is expected to finish by May 30.

Vietnam Railways said 22 tunnels on the north-south railway were constructed between 1927 and 1935, and the tunnels' walls had cracks.

"We carried out repairs at some tunnels since 2000," Vietnam Railways head Tran Thien Canh said. "Twelve tunnels need urgent upgrades, and we've allocated nearly VND4 trillion for the work during 2021-2025. We've also proposed to upgrade 27 other tunnels during the 2026-2030 period with an estimated investment of between VND2.50-3 trillion."