A top Senate Republican is warning that the federal Bureau of Prisons could be letting Muslim groups with terror ties vet chaplains and religious instructors, increasing the risk of indoctrination and radicalism behind bars. Senate Judiciary Committee Chairman Charles Grassley, R-Iowa, in a letter to the agency, flagged "recent revelations that the bureau enlisted an organization previously found to have ties to terrorist organizations" to screen potential Islamic chaplains. "It is imperative that the BOP take every measure possible to ensure the safety of its personnel within federal prisons and take all reasonable measures to ensure that Islamic extremism is...