A crude explosive device blew up in north-west Delhi on Saturday, injuring a man and his grandson.
However, police have ruled out a terrorist angle to the incident.
The device, lying in a garbage heap in an isolated area in Model Town, went off when Ram Murti (50) and his two-year-old grandson picked it up.
While Murti's right thumb was severed as a result of the blast, his grandson also sustained injuries and both had been hospitalised.
The two had apparently gone to the area to relieve themselves.
A senior police official said the device was probably abandoned by fishermen who used such crude bombs to kill fish in a stream nearby.
It was unlikely that terrorists were involved but investigations were on, he added.
