A roadside building collapses in Shanghai on April, 11, 2016. Rescuers have already pulled two people out o the debris. [Photo:weibo.com]

Dozens of rescuers are searching for more survivors after a woman and a child were pulled alive from a collapsed three-storey building in Shanghai, said government sources.

The roadside building in Songjiang District collapsed at 12:50 p.m. Monday.

The middle-aged woman and child have been taken to hospital.

A rescue operation is under way as detecting devices still show signs of life in the debris, said a rescuer at the scene.

The cause of the collapse is unclear.