Both the bombs contained home-made explosives, but yesterday's one contained less amount of explosive while it also had aluminium powder in it, said an expert yesterday after primary examination of the evidences of explosion.

The circuit used in yesterday's bomb was simple, but it was a completely different one in Tuesday's bomb, which was not found in any of those used in the recent blasts, the expert said requesting anonymity.

The bomb that went off yesterday weighed around one kilogram and contained pieces of iron used in fishing nets as splinters while the same kind of splinters weighing around three kilograms were collected from the site of Tuesday's blast.

The nature of the bombs blasted in Gazipur suggests that the same group is involved in manufacturing them, he said.

The primary investigation of yesterday's blast also revealed that the bomb was not tied with the bomber's body, who rather hurled it, the expert said.