'This is the biggest tragedy we have faced,' said her husband, himself in tears while he was trying to console her.

Some parents were wailing and some worried and confused about the whereabouts of their children.

'I have been looking for my son. But so far there has been no information,' said a man. He was told the boy had been taken to the Guru Tegh Bahadur Hospital.

'They are not allowing us inside nor are they telling us about our children,' a woman cried.

As feared, angry parents threw stones at the policemen and blocked traffic on the road but the situation was brought under control quickly.