A group of people at Gaadi Mohalla locality of Saidakadal took to streets and staged a demonstration in support of their demand for proper roads after two minor siblings drowned two days back, officials said.
They said some civil and police officials rushed to the scene and were persuading the protestors to disperse when all off a sudden the bridge collapsed.
Over 60 people on the bridge fell in the water and some 30 of them received injuries, the officials said, adding the injured were shifted to Rainawari hospital where condition of six of them was stated to be "serious".
Dozens of people were rescued and efforts are still on to ensure that nobody is still in the waters of the lake, they said.