The Colombian authorities have offered 500m pesos ($270,000; £175,000) reward for information leading to the arrest of people who detonated a car bomb in the capital, Bogota, on Thursday.
President Juan Manuel Santos announced the reward, and admitted he still did not know who carried out the bombing.
Some police officials have blamed left-wing rebels for the explosion.
The bomb injured nine people when it was detonated near the studios of a radio station in the north of Bogota.
The office block housing Caracol Radio was damaged and the windows of nearby buildings and cars were blown out.
It was not clear if the radio station was the target of the explosion.
Bomb attacks on Colombian cities decreased under Mr Santos' predecessor, Alvaro Uribe, who was president from 2002 until 7 August this year.
Mr Uribe pursued a hard-line stance against left-wing guerrilla groups such as the Farc, which has been fighting the Colombian government since the 1960s.