CARTAGENA, Colombia (CNN) -- Secret Service agents sent to Colombia ahead of President Barack Obama have been relieved of duty and returned home amid allegations of misconduct, officials said.
The incident in Cartagena was one of two security issues -- the other involved bomb blasts -- that overshadowed the start of the sixth Summit of the Americas, where the president was to focus on trade, energy and regional security with 33 of the region's 35 leaders.
The president arrived in the coastal resort city Friday, a visit that will mark the most time a U.S. president has spent in that country, where security concerns had limited previous presidential trips.
Within hours of the president's arrival, an undisclosed number of Secret Service agents were relieved of duty and replaced, said Edwin Donovan, an agency spokesman.
"There have been allegations of misconduct made against the Secret Service in Cartagena, Colombia, prior to the president's trip," Donovan said in a statement.
"Because of this, those personnel are being relieved of their assignments, returned to their place of duty, and are being replaced by other Secret Service personnel. The Secret Service takes all allegations of misconduct seriously."
Donovan declined to identify the nature of the alleged misconduct, saying only the mater was being turned over to the agency's internal affairs.
But Jon Adler, president of the Federal Law Enforcement Officers Association, told The Washington Post that the accusations relate to at least one agent having involvement with prostitutes in Cartagena.
CNN could not immediately confirm the claim.
Amid the reports that Secret Service agents were being replaced, two small blasts occurred nearly back-to-back in Cartagena.
The explosions, one near a bus station and another near a shopping mall, occurred well away from where the world leaders were gathering for the start of the summit, said Alberto Cantihho Toncell, a spokesman for the Colombia National Police.
There were no casualties, and only minor damage was reported, Toncell said.
The explosions came on the heels of a similar one earlier in the day near the U.S. Embassy in the capital city of Bogota, authorities said.
The blasts were a reminder of the violence that has gripped Colombia as it battled powerful cocaine drug cartels. Violence has significantly fallen off in recent years as the Bogota government, aided by U.S. extradition efforts, has successfully picked apart the cartels.
CNN's Chelsea J. Carter and journalist Jorge Baron contributed to this report.
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