Four people have been killed in a bomb explosion on a crowded bus in north-west Colombia. More than 30 others were injured in the blast, which happened on a rural road in the province of Antioquia. Police are investigating whether there was a bomb on the bus or if explosives went off as the bus drove past. The regional police commander blamed the attack on the country’s largest rebel group, the leftist Revolutionary Armed Forces of Colombia (FARC). Full Story