The police said they had arrested two of the three people believed to be responsible for the explosion, though they were unwilling to state why they had burst the bomb. Sources, however, said that the blast was the outcome of rivalry between two groups of migrant workers, who dominate the slum.

Senior police officials arrived at the spot soon after the bomb went off at lane no 12 of the slum around 3.45 p.m. While Shankar Deenbandhu Patra died on the spot, Kaanu Jayaram Sahu (9) and Nitu Gopinath Goud (10) were in danger of losing their sight, doctors at the New Civil Hospital said.

All the three victims were within five feet of the bomb when it exploded in a narrow three-feet-wide lane. In all possibility, the bomb was not meant for the victims, sources said.

The police said three people -- Krishna Ranganath Subuddhi (15), Bhagwan Kirtan Subuddhi (27) and Lathu Kishan Vrindavan (30), all residents of the slum -- had been identified as responsible for the explosion. While the first two had been arrested and had admitted their guilt, Vrindavan was absconding, they added.

Two others could also be involved in the explosion, sources said, adding, however, that their identities had not yet been determined.

Elaborating on the possible motive behind the explosion, sources said some time ago, one Shambhu and one Subuddhi had had a personal quarrel, following which Shambhu threatened the latter with a country revolver. He was subsequently arrested, but jumped custody and fled to his native village in Orissa.

The police said the three accused and possibly the two others were all from Shambhu's village and could have been trying to settle scores. The arrested are under interrogation at present.

Meanwhile, hospital sources said the condition of both the survivors was critical. A number of small nails and particles had got embedded in their bodies, and were removed in a series of operations late on Thursday evening. However, doctors said both of Nitu's hands had been almost torn off by the explosion, while both boys are in danger of losing their sight.

Though the precise nature of the bomb is still being investigated, sources said it was probably made up of explosives, nails and string.