Employees of Subway Line 5 were left red-faced on Monday afternoon after all the passenger information screens at stations showed a phrase including Chinese curse words.

Passengers posted pictures of the screens on microblogs Monday afternoon, which said "Wang Peng, your sister." "Your sister" is a Chinese way of cursing somebody.

Subway employees later pasted newspapers on the screens to cover up the rude phrase, and Beijing Subway replied on its Sina microblog that the screens were being upgraded, and they are investigating the cause of the snafu.