The brother of Colombia's foreign minister has been arrested on suspicion of ties with paramilitaries involved in the country's drug trade.
Mr Araujo was arrested at a restaurant in Bogota
Senator Alvaro Araujo is the highest ranking politician to be arrested as part of the investigation.
Further warrants have been issued for five other lawmakers allied to President Alvaro Uribe.
Three other lawmakers were jailed in November for links to paramilitaries fighting leftwing rebel groups.
"This arrest is of the utmost gravity, as it reflects the penetration of paramilitary power into Uribe's closest circles," Jose Miguel Vivanco, of New York-based Human Right Watch said.
The paramilitary groups began as private militias in the 1980s to protect property from being seized by leftist rebels.
Despite the scandal, the president's popularity remains at 70%, according to recent opinion polls.
Some of the evidence against politicians came from a laptop belonging to a senior paramilitary warlord known as Jorge 40, or Rodrigo Tovar Pupo.
Analysts say that the arrests are encouraging as they show increasing transparency in Colombian politics.
"Everyone knew the paramilitaries had infiltrated Congress," said Pablo Casas of Colombian think-tank Security and Democracy.
"The good news is that the justice system is showing a certain level of independence."