The US Federal Bureau of Investigations, FBI, and the Central Intelligence Agency, CIA, are working on two main leads in the Boston Marathon deadly blast that killed three and injured over 140, some seriously.

According to the French Le Figaro, the leads are the terror attack being perpetrated by far-right activists or an isolated jihadist.

The probe is also revolving around the symbolic of the date of the attack as Monday April 15 was celebrated as Patriots' Day in Massachusetts (the first battles of the American Revolutionary War). It was also the deadline for all Americans to file their tax declarations. The latter is seen as a hint the perpetrators oppose Washington's fiscal policies, thus the theory they could be an extreme-right group.

On the other hand side, the attack bears the marks of a terrorist group like al-Qaida. According to undisclosed sources, the devices have not been so well made to presume the participation of an entire terrorist organization.