A pivotal subway route linking southern and northern Beijing suspended operation for about 13 minutes during the rush hour Wednesday morning, stranding thousands of people on their way to work.

A spokesman of the Beijing subway operators said the cause of the shutdown was not immediately known.

The shutdown was reported at around 8 a.m. on line 4, he said.

Line 4 is the newest subway line in Beijing's underground transportation network. It opened on September 28, linking Beijing's populous yet underdeveloped southern areas with the city center and the developed western areas.