Barbara Bush's purse and cell phone were taken while she was dining in a Buenos Aires restaurant.
La Nacion newspaper, citing anonymous government sources, said in its online edition early Wednesday that one of Mr. Bush's daughters had her purse taken Sunday afternoon in the popular tourist district of San Telmo.
A pair of thieves removed the purse from under a table while Secret Service agents stood guard at a distance, La Nacion reported.
Should the Secret Service have chased the guy? Absolutely not, former agent Chuck Vance told CBS News correspondent Wyatt Andrews. Vance said the theft may have been a diversion and the greater danger was a possible kidnapping.
"Their response is to the protectee, to be with the protectee, not to give chase," Vance said.
Argentine police told The Associated Press they had no complaint of any such incident on file, and the U.S. Embassy in Buenos Aires said it would have no comment. In Washington, the White House, Secret Service and State Department also declined comment.
CNN cited a law-enforcement source who was briefed on the incident as saying that "at no point were the protectees out of visual contact and at no point was there any risk of harm."
Argentina's largest-circulation daily, Clarin, ran an online report citing the government news agency Telam as saying that Barbara Bush had her purse taken along with a cell phone that was inside it. Telam cited an official source who did not wish to be identified by name and who provided no other details.
Barbara and her twin sister, Jenna, will turn 25 on Saturday.
Jenna visited neighboring Paraguay last month to take part in a UNICEF program for young professionals.
This wasn't the only troubling incident on the twins' trip to Argentina: a Secret Service agent on the advance detail got into an altercation with someone after a night out and was badly beaten, according ABC News. The incident, described as an attempted mugging, happened while the agent was spending time on his own, the Secret Service told ABC.