A platform door at a Shanghai Metro subway station broke into pieces on its own, about 7:00 am Tuesday, xinmin.cn reports.

A broken subway platform door is cordoned off at the Laoximen station of Shanghai Metro's Line 8 on July 19, 2011. [Photo/weibo.com]

The Laoximen station, where the incident occurred, is a transfer station between Lines 8 and 10 on Shanghai Metro.

No one was injured at the site, but it raised the public's concerns over the safety of the metro platform door, as it is the second time this happened in the past six days in the city, with metro authorities still giving no explanation for them.

On July 14, another subway platform door broke at the Paobu Xincun station, much the same way as Tuesday's incident.