A week after a Secret Service prostitution scandal began unfolding in the hallway of a Colombian hotel, six agents have lost their jobs and hundreds of people have been interviewed.

The agency said Friday that three officers had resigned -- and that news came days after two supervisors and another officer were forced out. Also, the agency's director briefed President Barack Obama in the Oval Office on the latest developments.

A government official briefed on the investigation said more than 200 people have been interviewed so far. The official spoke on the condition of anonymity to discuss the continuing investigation.

Late Friday, Sen. Chuck Grassley urged a broader investigation, including checking hotel records for White House advance staff and communications personnel who were in Colombia for a regional summit.

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