Less than a year into operation, the high-speed rail route connecting Shanghai to Kunming in southwestern Yunnan province has been found to have safety issues that could have endangered the lives of passengers, media reported Tuesday.

China’s national rail operator told The Paper that it had found several train tunnels cutting through the hilly terrain of southwest China’s Guizhou province to be substandard.

According to The Paper, China Railway has reprimanded four companies involved in the construction, supervision, and design of the Guizhou section, as well as a third-party inspection firm, and issued various penalties. The main contractor held responsible, China Railway 20 Bureau Group, has been barred from bidding on national rail projects for the next year and will be held liable for 90 percent of the cost of repairs, while two other companies will shoulder 5 percent each.

A local news blogger in Guizhou was among the first to expose the route’s safety issues on Monday. In a Weibo microblog post that has since been deleted, he shared photos of shoddy construction in one of the tunnels and leaked internal documents from China Railway noting several accidents between June and July that prompted the company to start an investigation. The blogger also accused rail contractors of corruption.

The Shanghai-Kunming train connecting China’s financial hub with popular tourist sites in the country’s southwest began operation in December 2016 at a top speed of 300 kilometers per hour. But according to the blogger’s post, the service reduced its speed to 70 kilometers per hour while passing over the North Pan Jian Bridge in Guizhou due to safety concerns.

China’s high-speed rail network has seen explosive growth over the last decade, shortening travel times across the country and offering stiff competition to airlines. But authorities slammed the brakes after a deadly 2011 train crash in the southeastern city of Wenzhou, near Shanghai, which was blamed on mismanagement and design flaws.

From August 2011, a month after the accident, train speeds across the country were reduced. But two months ago — more than six years after the crash — China launched new bullet trains that zip between Shanghai and Beijing at 350 kilometers per hour.

Slower-speed subway systems have also had their share of troubles. In March, a whistleblower’s exposé on social media prompted authorities in Xi’an to replace 30 million yuan ($4.5 million) worth of faulty wiring through the northwestern city’s metro lines. Contractors constructing the subway in Chengdu, in southwestern China, also announced that they would replace cables from the same company.

Contributions: Qian Zhecheng; editor: Qian Jinghua.

(Header image: A high-speed train travels along newly built track during a test run in Anshun, Guizhou province, Sept. 21, 2016. Lu Wei/VCG)