The Shanghai Railway Bureau said it was still uncertain about the origin of bedbugs discovered on a high-speed train from Beijing to Shanghai, the Beijing News reported on Wednesday.

A passenger said on his Sina Weibo account that he was bitten by bedbugs in a high-speed train sleeper en route from Beijing to Shanghai on Aug 28.

He released a video on the Internet, displaying the bedbugs on the sheets and itch marks on his arm.

The passenger complained about sanitary conditions on the train.

The Shanghai Railway Bureau, operators of the train, said bedding in sleepers on all high-speed trains were always washed and disinfected after each journey.

An official of the bureau was quoted as saying that the bureau cannot be sure where the bedbugs came from but they were sure that all high-speed trains were cleaned and disinfected before embarkation.