One of a dozen provincial lawmakers kidnapped by the country's main rebel group a decade ago has been arrested for allegedly helping the insurgents plan the daring daylight abduction.

Colombians were stunned Thursday by the arrest of Sigifredo Lopez, 48, on suspicion of murder, treachery and hostage-taking. The news was especially alarming because he was the only one among the 12 who escaped execution by rebels in 2007 under circumstances that remain unclear.

Authorities have not mentioned a possible motive.

Lopez has said he survived because he was at a different but nearby location when the rebels committed the killings, mistakenly confusing for a military patrol another rebel group that neared the camp without notification.

Rebels of the leftist Revolutionary Armed Forces of Colombia, or FARC, had standing orders to kill their hostages rather than allow them to be rescued.

Lopez has said he was held by himself for the next two years until February 2009, when he became the last politician freed by FARC.

He said at the time that he owned his survival "to a miracle of God."

"I hope that there is some confusion, or this is a mistake," Diego Quintero, the brother of one of the slain deputies, said on Thursday.

He said he was led to believe from comments in a proof-of-life video of his brother, Alberto Quintero, that his brother and Lopez were never held together.

Lopez was arrested in Colombia's third-largest city of Cali, where he and the other were seized in 2002 from the provincial assembly building by rebels disguised as security force members.

Officials in Colombia's chief prosecutor's office said Lopez had helped the FARC plan the mass kidnapping.

They said various former guerrillas had provided testimony that Lopez participated. The officials spoke on condition of anonymity because they were not authorized to make public statements.

One official said prosecutors had video of a man believed to be Lopez offering detailed instructions on how to perpetrate the crime.

In the video, the man's face is not fully visible in the video but his voice can be heard, according the radio station, La FM.

It said the video came from computers seized in November when the military killed the rebels' top leader, Alfonso Cano.

La FM said the man appearing in the video explains where each deputy would be, the hours they came and went, and where the building's security cameras were located as well as also noting that none of the deputies carried weapons.

Lopez unsuccessfully ran for Colombia's Senate and Cali's mayor's office last year on the Liberal Party ticket.

The party's chief, Simon Gaviria, called the accusations against Lopez "macabre" and said he would ask the party's ethics committee to suspend Lopez.