A Beijing-Shanghai high-speed train was forced to decelerate Monday because a passenger smoking in a toilet set off an alarm, the Beijing News reported on Tuesday.

The incident at about 4:45 pm near Dezhou, Shandong Province, did not delay the train, which was headed to the Beijing South Railway Station from Shanghai Hongqiao Railway Station.

When the alarm went off, the speed of the train suddenly dropped from 310 kilometers per hour to 280 kilometers per hour. A man aged about 40 was spotted by a train employee having a smoke in a toilet between coaches 9 and 10, according to the report. The train slowed to a near stop but continued moving, a witness named Wu Huiyang recalled to the paper.

The smoker was taken away, criticized by train police and fined 50 yuan (US$7.73), according to the Beijing News.

"Smoking bans on high-speed trains should be strictly followed," an anonymous official from the Ministry of Railways told the Global Times on Tuesday.

"The monitoring system on trains can detect smoke quickly, and then the operating system automatically slows down the train," he said.

"Coaches of high-speed trains are fully enclosed in order to prevent passengers from enduring the extremely loud noise generated by high-speed movement, therefore, smoking is banned even in the toilets and the sections linking carriages," the official explained.

Other trains permit smoking in toilets and in the space between cars, but ban it in air-conditioned carriages, he said.

In another case, a passenger was caught smoking in a toilet after alarms sounded on a high-speed train from Beijing to Shanghai on July 2. Punishments vary according to the railway departments in different cities, the official said.

"The bans on indoor smoking in public areas cannot be applied in trains," Cui Xiaobo, a Capital Medical University professor and draftsman for regulations banning smoking in public and indoor areas in Beijing, told the Global Times on Tuesday.

"Smoking in high-speed trains is related to China's fire protection laws and the Law of the People's Republic of China on Public Security Administration Punishments," he said.