By Will Grant

BBC News, Miami



The 27-year-old woman was travelling to the western region of Valle del Cauca, when police conducted a routine check.

The woman had almost 800 explosives attached to her which the authorities believe she was transporting to forces of the left-wing rebel army, the Farc.

It is still unclear whether she was doing so for payment or under duress.

When police searched the woman, they found she had a large quantity of explosives strapped to her body. In total, there were 790 bomblets fixed to her, which police say were sufficient to have destroyed the bus and most likely killed everybody on board.

The woman, however, was not a suicide bomber - something which remains almost unheard of in Colombia's 40-year-long civil war.

Instead, she was transporting the material to members of the left-wing rebel group, the Farc, operating in Valle del Cauca.

The group has been known to use all sorts of methods to both transport explosives and carry out bomb attacks, sometimes involving people who unwittingly act as agents.

Indeed, the authorities attribute one of the most notorious Farc attacks in recent years - the 2003 bombing of El Nogal nightclub in Bogota which left 36 people dead - to a similar situation.