WASHINGTON — A senior Senate Republican said Tuesday the head of the Secret Service is seeking an independent probe of an incident involving prostitutes and Service personnel in Colombia.

Iowa Sen. Charles Grassley says Secret Service Director Mark Sullivan told him Tuesday that he’s referred the matter to the agency’s inspector general.

Other lawmakers Sullivan met with on Tuesday say he reports getting conflicting accounts about whether the 20 or 21 women who met with Secret Service members and military personnel in Cartagena were prostitutes.