Garda Commissioner Martin Callinan said today that the bomb discovered in the Phoenix Park yesterday is not the usual type of explosive device used by Dublin criminals.
The device was made safe yesterday after army bomb disposal experts were called in.
The bomb, thought to be in the region of 20 kilos in weight, has not yet been claimed by any dissident group.
"This isn't the normal improvised explosive device that we've seen in more recent times associated with the criminal fraternity," said Commissioner Martin Callinan.
"Nobody has claimed ownership of that device and we're working very, very hard to try and establish who is responsible."