"A loud roar and the heavens seemed to have crumbled over us. Thick clouds of dust streamed into the compartment leaving me gasping for breath," is how Anil Yadav, one of the passengers on the train over which a bridge fell on Saturday morning, describes the moment when the mishap occurred.

The accident, which occurred in Bihar's Bhagalpur district, left at least 20 people dead and 18 wounded.

Eyewitnesses and survivors said it was 7.50 am when the bridge, which was being dismantled, collapsed on the Howrah-Jamalpur super-fast Train No. 3071.

A portion of the 150year-old bridge, curiously named ulta pul (in Hindi, ulta means upside down and pul means bridge), came crashing down on the S-8 sleeper class coach.

The falling debris smashed half the coach, which was 11th from the engine, badly, and caused the train to derail.

"As the train was about to reach the station I, along with several others, was standing at the gate when suddenly we heard a noise resembling thunder and saw half the coach on the opposite end crumble under the impact. I jumped out in horror," said a visibly upset Manju Rai, who had boarded the train at Ghogha for Bhagalpur.

Soon, hundreds of people gathered at the scene and, before official help could reach the victims, many began digging into the debris with bare hands to pull out the trapped passengers.

"I, and many others like me who had reached the place to enquire, had pulled out eight to nine injured passengers by the time the first ambulance arrived and sent them to hospitals," said Rahul Kumar, a volunteer helping the administration in rescue efforts.

A bulldozer arrived on the scene about an hour after the mishap to clear the debris but the locals complained that it was too small to make a difference to the rescue operations.

The efforts to remove the debris began in right earnest a couple of hours after the mishap when more powerful excavating machines arrived.

"The railway authorities are solely responsible for the tragedy. They allowed a train to pass under the bridge which could have crumbled any time," said an agitated Ram Kumar.

"They have played with the lives of innocent passengers. Now, they should ensure that those injured get proper medical attention at railways' cost," he said.

On November 30, at around 10.50 pm, while the dismantling work of the first and second arches of the bridge was going on, portions of it had fallen down blocking the railway track and obstructing train movement.

Though the Railways had pulled down the two arches, the last span that was left standing collapsed on Saturday morning, about 24 hours after traffic had resumed on the track at 7.30 am on Friday.