The U.S. Secret Service is investigating allegations of improper conduct last year by personnel sent to El Salvador that mirror the behavior by employees implicated in the agency’s Colombia sex scandal, according to a lawmaker closely tracking the agency’s investigations.

But House Homeland Security Committee Chairman Peter T. King (R-N.Y.) cautioned that the new inquiry is just part of the agency’s broad investigation into whether agents and officers have interacted with prostitutes in the past.

“It doesn’t mean that there’s any validity to it,” King said Thursday of the new inquiry into allegations that Secret Service personnel behaved inappropriately on a trip last year to El Salvador. “They’re looking into all allegations.”

KIRO-TV in Seattle first reported Wednesday night on the El Salvador trip.

If the allegations are true, they would appear to contradict statements made Wednesday by Homeland Security Secretary Janet Napolitano that the Secret Service was unaware of any behavior similar to the Colombia incident having occurred in the past 2 1 / 2 years.

Also Thursday, the Pentagon confirmed that it has expanded its probe into the Colombia scandal by adding a 12th member of the military to the list of personnel under investigation.

The U.S. Southern Command said it has instructed military investigators to probe the actions of a 12th individual, who was assigned to the Military District of Washington with duty at the White House Communications Agency. The soldier has since been reassigned to other duties pending the outcome of the investigation, said military spokesman Jose Ruiz.

King said Thursday that the Secret Service Office of Professional Responsibility had no record of formal allegations against personnel sent last year to El Salvador.

Asked Thursday what should be done if it turns out that the unfolding prostitution scandal represents a recurring Secret Service problem, Senate Majority Leader Harry M. Reid (D-Nev.) had a simple answer: “Hire more females.”

Staff writer Rosalind S. Helderman contributed to this report.