Venezuelan President Nicolas Maduro was expected to make his first public appearance today since being targeted over the weekend by drones that he said were sent to "assassinate" him during a military parade.
Santos, who hands over power to elected successor Ivan Duque tomorrow, has categorically rejected the accusation.
A live broadcast of the incident on Venezuelan state television showed Maduro interrupted in mid-speech by an explosion and looking up in confusion.
Dozens of soldiers on parade are then seen breaking ranks and running away in panic.
Maduro and his government said the president had been targeted by two flying drones carrying explosives.
They blamed the attack on Colombia, working with the "ultra far-right" Venezuelan opposition, and financed by unnamed figures in the US state of Florida.
Venezuelan Attorney General Tarek William Saab told a news conference on Monday that several suspects were in custody and authorities "will pursue under the law all those who conspire against public peace." He said the drone attack was "an attempted massacre." Seven soldiers were wounded.
"All the material perpetrators of the act and their accomplices have been identified," Saab said.
He added that two of the suspects were "caught in the act" guiding one of the drones from a car close to the parade.
He said two drones had been used, each carrying a kilogram of C4 explosive.
One went out of control and flew into a building, and the other was jammed and exploded before reaching the president's podium, Reverol said. Maduro's supporters marched through Caracas today.
The 55-year-old Socialist leader was expected to appear in public to address them.
Several questions hover over Saturday's incident, with some inconsistent information coming from various sources.
No drones could be seen in Saturday's broadcast, which was cut moments after the soldiers were seen scattering away from dias where Maduro was standing flanked by military chiefs and his wife.
Some accounts on the ground said a fire at a nearby building was caused by the accidental explosion of a gas cylinder.
An unauthenticated statement from a rebel group calling itself the "National Movement of Soldiers in T-Shirts" claimed responsibility in a statement passed to an opposition journalist based in the US.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)