The bizarre case surfaced Monday, when a Colombian television station aired
                 footage of a May ceremony at Bogota's National Museum at which Colombian
                 President Andres Pastrana and Venezuelan President Hugo Chavez were seated
                 together at a table.

                 Helping to push in Chavez's chair and then standing behind the two leaders during
                 the ceremony was a thin man with glasses and a dark, rumpled suit. His presence,
                 apparently as part of the security detail, raised no suspicions at the time.

                 But on closer inspection, the man behind the presidents is the same man Colombia's
                 secret service presented to the media earlier this month as an alleged guerrilla
                 deserter who revealed an assassination plot against a Colombian presidential
                 candidate, Alvaro Uribe.

                 Colombian and Venezuelan authorities have been unable to explain how this man,
                 identified as Diego Serna, a former seminary student turned rebel, wound up being
                 next to the two heads of state. Members of the Colombian congress have
                 summoned the interior minister and the head of the secret service agency to a
                 closed-door session next week to demand answers.

                 Chavez arrived Tuesday in Bogota for a new visit and faced a barrage of questions.
                 The left-leaning Venezuelan president is a friend of Cuban President Fidel Castro
                 and has previously been accused of sympathizing with Colombia's guerrillas.

                 But Chavez said he had no idea who Serna was and pointed out that Colombia's
                 government was in charge of all the security for his visit in May. Airing the video
                 showing Serna with Pastrana and Chavez the night before the Venezuelan leader's
                 arrival Tuesday suggested "enemies" were trying to spoil relations with Colombia,
                 Chavez told reporters.

                 Since the story broke, the secret service has released additional excerpts from its
                 original questioning of Serna about the alleged plot against Uribe. In the video,
                 Serna claims that during Chavez's May visit, he was part of a rebel assassination
                 plot to kill Pastrana.

                 On Friday, another television station broadcast footage of a younger Serna wearing
                 a cowboy hat and jeans and standing in the background at a 1990 ceremony at
                 which another rebel group, the M-19, laid down its arms under a peace agreement.

                 Former M-19 rebels interviewed on local television said Serna was never a guerrilla
                 member. They said he was a sympathizer known as "the priest."

                 The Revolutionary Armed Forces of Colombia, or FARC, also denies Serna is a
                 member of Colombia's largest rebel group. It has said the accusations that he was
                 part of a guerrilla assassination plot are aimed at slandering the rebels.

                 The government, for its part, hasn't explained how Serna got so close to the two
                 presidents. Pastrana has said only that his government is investigating.

                 The man identified as Serna has not spoken to the media. Now, even his
                 whereabouts are a mystery.

                 Secret service officials said Friday he was in a witness protection program
                 managed by the federal prosecutors' office. Federal prosecutors said they don't
                 have him, and insist he is being held by the secret service.

                  Copyright 2001 The Associated Press.