The suspect, identified as Jesus Santrich, was arrested on Monday in Colombia on drug trafficking charges, Santos said in a message issued by his government.

"If due process is fulfilled -- and if there is irrefutable evidence -- then there are grounds for extradition for crimes committed since the signing of the (peace) accord, and I will not stay my hand in authorizing that," Santos said.

The landmark peace deal between the FARC and Santos's government was signed in November 2016, putting an end to a half century of conflict.

Since then, the FARC has disarmed and transformed itself into a political party, swapping its crossed-rifles emblem for a red rose. Ten of its members were given allotted seats in Congress.

Some dissident members of the FARC are said to have turned to drug trafficking and other criminal endeavors.

Under the peace accord, repentant FARC fighters were required to confess their wartime crimes and pay reparations to victims to avoid jail. But they could still be arrested for any crimes they committed after the deal.