A US Army probe into the alleged killing of several Iraqi civilian detainees by four US soldiers in 2007 entered its second day Wednesday as investigators weighed whether to take the case to the next step. Witness testimony at a pretrial Article 32 Court Martial hearing at US Rose Barracks opened Tuesday with questioning of four members of the 172nd Infantry Brigade whom prosecutors allege conspired to commit the premeditated murder of a group of Iraqi detainees in Iraq between March 10 and April 16, 2007. Staff Sgt. Jess Cunningham, Sgt. Charles Quigley, Spc. Steven Ribordy and Spc. Belmor Ramos are being investigated. Ribordy and Ramos both waived their right to have an Article 32 investigation prior to the proceedings Tuesday, indicating they had struck some sort of plea deal, though none was mentioned. In testimony on Tuesday, Sgt. Daniel Evoy and Spc. Humberto Navarro said four Iraqi detainees killed near Baghdad in 2007, but another witness, Spc. Joshua Hartson, recalled there being five detainees.