The Longhai railway, one of China's major east-west rail lines, resumed operations on Monday morning after the Gansu province section was blocked for several hours due to a chemical leak, the Ministry of Railways said.

According to a statement on the ministry's website, a tank wagon carrying silicon tetrachloride, a strong acid, broke down on the 316 national highway in Wushan county in Gansu province at 4:40 pm on Sunday. The chemical leaked from the vehicle, producing large amounts of white mist after it reacted with rain.

The diffused emissions damaged power supply equipment on the nearby Longhai line that runs parallel to the highway, the ministry said. Three passenger trains near that section of the railway were forced to stop, blocking the 1,759-km line from Lanzhou in Gansu province to Lianyungang in Jiangsu province.

The Ministry of Railways said the three trains were about 3 km from the leak. All the trains were pulled into nearby stations by diesel locomotives to ensure passengers' safety.

Four drivers on the highway, who were at risk of being poisoned by the chemical mist, were sent to hospital for health checks, according to China Central Television. No casualties have been reported.

A netizen named Li Sibei, who claimed to be on the stopped T114 train from Lanzhou, said on her micro blog the train had been delayed for at least five hours.

"The train crew should have informed us passengers about what was happening straightaway, but they failed to do so, which annoyed me a lot," Li wrote on her micro blog.

According to the Railways Ministry, the Longhai line, whose power grid was crippled by the chemical mist, was 70 meters from the source of the leak.

Two weeks ago, the public became concerned when it was revealed that a high-speed railway project under construction was as close as 5.8 meters from a highway in Zhuji city, Zhejiang province.

Shuai Bin, deputy dean of the School of Traffic and Logistics at Southwest Jiaotong University, told China Daily the distance between the highway and the Longhai line is in accordance with the nation's construction regulations.

Although Shuai considered the accident in Wushan a rare event, he said safety issues related to the transport of dangerous goods should be taken seriously.

"The railway authorities should develop contingency plans for dealing with emergencies in the transporting of dangerous cargo, including how to organize professional rescue teams," he said.

"Meanwhile, road inspection regulations should be strengthened to prevent vehicles from illegally carrying dangerous substances."

The Longhai railway, which connects Lianyungang on the Yellow Sea with Lanzhou through Jiangsu, Anhui, Henan, Shaanxi and Gansu provinces, is one of the busiest railways in China and a central section in the New Eurasian Land Bridge.